diff --git a/backend/app/models/alert.py b/backend/app/models/alert.py
index 97fea83..fb88470 100644
--- a/backend/app/models/alert.py
+++ b/backend/app/models/alert.py
@@ -1,7 +1,7 @@
 import uuid
 from datetime import datetime
 
-from sqlalchemy import String, Boolean, Float, ForeignKey, Index, func, Text
+from sqlalchemy import String, Boolean, Float, ForeignKey, Index, func, Text, DateTime
 from sqlalchemy import Uuid, JSON
 from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.orm import Mapped, mapped_column, relationship
@@ -58,6 +58,7 @@ class Alert(Base):
         Boolean, default=False, nullable=False,
     )
     created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
diff --git a/backend/app/models/alert_setting.py b/backend/app/models/alert_setting.py
index c745c49..30ddca7 100644
--- a/backend/app/models/alert_setting.py
+++ b/backend/app/models/alert_setting.py
@@ -1,7 +1,7 @@
 import uuid
 from datetime import datetime
 
-from sqlalchemy import String, Boolean, Float, ForeignKey, Index, func
+from sqlalchemy import String, Boolean, Float, ForeignKey, Index, func, DateTime
 from sqlalchemy import Uuid
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
@@ -39,10 +39,12 @@ class AlertSetting(Base):
         comment="阈值（如评分下降超过5分触发）",
     )
     created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
     updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         onupdate=func.now(),
         nullable=False,
diff --git a/backend/app/models/knowledge.py b/backend/app/models/knowledge.py
index 950a0b9..31cff5b 100644
--- a/backend/app/models/knowledge.py
+++ b/backend/app/models/knowledge.py
@@ -1,7 +1,7 @@
 import uuid
 from datetime import datetime
 
-from sqlalchemy import String, Integer, ForeignKey, Index, func, Text
+from sqlalchemy import String, Integer, ForeignKey, Index, func, Text, DateTime
 from sqlalchemy import Uuid
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
@@ -42,10 +42,12 @@ class KnowledgeBase(Base):
         nullable=True,
     )
     created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
     updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         onupdate=func.now(),
         nullable=False,
@@ -93,10 +95,12 @@ class KnowledgeDocument(Base):
     # mapped_column("metadata") to avoid SQLAlchemy reserved keyword conflict
     extra_metadata: Mapped[dict | None] = mapped_column("metadata", JSONType, nullable=True)
     created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
     updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         onupdate=func.now(),
         nullable=False,
@@ -153,6 +157,7 @@ class KnowledgeChunk(Base):
     # mapped_column("metadata") to avoid SQLAlchemy reserved keyword conflict
     extra_metadata: Mapped[dict | None] = mapped_column("metadata", JSONType, nullable=True)
     created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
@@ -192,6 +197,7 @@ class KnowledgeSearchLog(Base):
     results_count: Mapped[int] = mapped_column(Integer, server_default="0", nullable=False)
     latency_ms: Mapped[int] = mapped_column(Integer, server_default="0", nullable=False)
     created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
diff --git a/backend/app/models/knowledge_graph.py b/backend/app/models/knowledge_graph.py
index fb8550d..885b189 100644
--- a/backend/app/models/knowledge_graph.py
+++ b/backend/app/models/knowledge_graph.py
@@ -83,10 +83,12 @@ class KnowledgeEntity(Base):
 
     # 元数据
     created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
     updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         onupdate=func.now(),
         nullable=False,
@@ -151,6 +153,7 @@ class KnowledgeRelation(Base):
 
     # 元数据
     created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
diff --git a/backend/app/models/lifecycle.py b/backend/app/models/lifecycle.py
index f79fbaf..53846c6 100644
--- a/backend/app/models/lifecycle.py
+++ b/backend/app/models/lifecycle.py
@@ -1,7 +1,7 @@
 import uuid
 from datetime import datetime
 
-from sqlalchemy import String, Integer, ForeignKey, Index, func, Text
+from sqlalchemy import String, Integer, ForeignKey, Index, func, Text, DateTime
 from sqlalchemy import Uuid
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
@@ -31,10 +31,12 @@ class LifecycleProject(Base):
         nullable=True,
     )
     created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
     updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         onupdate=func.now(),
         nullable=False,
@@ -73,8 +75,8 @@ class ProjectStage(Base):
     )
     stage_number: Mapped[int] = mapped_column(Integer, nullable=False)
     status: Mapped[str] = mapped_column(String(20), server_default="pending", nullable=False)
-    started_at: Mapped[datetime | None] = mapped_column(nullable=True)
-    completed_at: Mapped[datetime | None] = mapped_column(nullable=True)
+    started_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
+    completed_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
     notes: Mapped[str | None] = mapped_column(Text, nullable=True)
     metrics: Mapped[dict | None] = mapped_column(JSONType, nullable=True)
 
diff --git a/backend/app/models/monitoring_record.py b/backend/app/models/monitoring_record.py
deleted file mode 100644
index 8662c57..0000000
--- a/backend/app/models/monitoring_record.py
+++ /dev/null
@@ -1,108 +0,0 @@
-import uuid
-from datetime import datetime
-
-from sqlalchemy import String, Integer, Float, ForeignKey, Index, func
-from sqlalchemy import Uuid
-from sqlalchemy.orm import Mapped, mapped_column, relationship
-
-from app.database import Base, JSONType
-
-
-class MonitoringRecord(Base):
-    __tablename__ = "monitoring_records"
-
-    id: Mapped[uuid.UUID] = mapped_column(
-        Uuid(as_uuid=True),
-        primary_key=True,
-        default=uuid.uuid4,
-    )
-    user_id: Mapped[str] = mapped_column(
-        String(36),
-        ForeignKey("users.id", ondelete="CASCADE"),
-        nullable=False,
-    )
-    brand_id: Mapped[uuid.UUID] = mapped_column(
-        Uuid(as_uuid=True),
-        ForeignKey("brands.id", ondelete="CASCADE"),
-        nullable=False,
-    )
-    content_id: Mapped[uuid.UUID | None] = mapped_column(
-        Uuid(as_uuid=True),
-        ForeignKey("contents.id", ondelete="SET NULL"),
-        nullable=True,
-    )
-    query_id: Mapped[uuid.UUID | None] = mapped_column(
-        Uuid(as_uuid=True),
-        ForeignKey("queries.id", ondelete="SET NULL"),
-        nullable=True,
-    )
-    task_type: Mapped[str] = mapped_column(String(50), nullable=False)
-    status: Mapped[str] = mapped_column(
-        String(20), server_default="pending", nullable=False,
-    )
-    baseline_data: Mapped[dict | None] = mapped_column(JSONType, nullable=True)
-    current_data: Mapped[dict | None] = mapped_column(JSONType, nullable=True)
-    change_report: Mapped[dict | None] = mapped_column(JSONType, nullable=True)
-    interval_hours: Mapped[int] = mapped_column(
-        Integer, server_default="24", nullable=False,
-    )
-    last_checked_at: Mapped[datetime | None] = mapped_column(nullable=True)
-    next_check_at: Mapped[datetime | None] = mapped_column(nullable=True)
-    created_at: Mapped[datetime] = mapped_column(
-        server_default=func.now(),
-        nullable=False,
-    )
-    updated_at: Mapped[datetime] = mapped_column(
-        server_default=func.now(),
-        onupdate=func.now(),
-        nullable=False,
-    )
-
-    brand: Mapped["Brand"] = relationship("Brand")
-    user: Mapped["User"] = relationship("User")
-
-    __table_args__ = (
-        Index("idx_monitoring_records_user_id", "user_id"),
-        Index("idx_monitoring_records_brand_id", "brand_id"),
-        Index("idx_monitoring_records_status", "status"),
-        Index("idx_monitoring_records_next_check_at", "next_check_at"),
-    )
-
-
-class ContentBaseline(Base):
-    __tablename__ = "content_baselines"
-
-    id: Mapped[uuid.UUID] = mapped_column(
-        Uuid(as_uuid=True),
-        primary_key=True,
-        default=uuid.uuid4,
-    )
-    brand_id: Mapped[uuid.UUID] = mapped_column(
-        Uuid(as_uuid=True),
-        ForeignKey("brands.id", ondelete="CASCADE"),
-        nullable=False,
-    )
-    content_id: Mapped[uuid.UUID | None] = mapped_column(
-        Uuid(as_uuid=True),
-        ForeignKey("contents.id", ondelete="SET NULL"),
-        nullable=True,
-    )
-    citation_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-    positive_ratio: Mapped[float] = mapped_column(Float, nullable=False, default=0.0)
-    avg_rank: Mapped[float] = mapped_column(Float, nullable=False, default=0.0)
-    platform_data: Mapped[dict | None] = mapped_column(JSONType, nullable=True)
-    recorded_at: Mapped[datetime] = mapped_column(
-        server_default=func.now(),
-        nullable=False,
-    )
-    created_at: Mapped[datetime] = mapped_column(
-        server_default=func.now(),
-        nullable=False,
-    )
-
-    brand: Mapped["Brand"] = relationship("Brand")
-
-    __table_args__ = (
-        Index("idx_content_baselines_brand_id", "brand_id"),
-        Index("idx_content_baselines_content_id", "content_id"),
-    )
diff --git a/backend/app/models/organization.py b/backend/app/models/organization.py
index d472520..16a33fa 100644
--- a/backend/app/models/organization.py
+++ b/backend/app/models/organization.py
@@ -1,7 +1,7 @@
 import uuid
 from datetime import datetime
 
-from sqlalchemy import String, Integer, ForeignKey, Index, func, Text
+from sqlalchemy import String, Integer, ForeignKey, Index, func, Text, DateTime
 from sqlalchemy import Uuid
 from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.orm import Mapped, mapped_column, relationship
@@ -24,10 +24,12 @@ class Organization(Base):
     plan: Mapped[str] = mapped_column(String(20), server_default="free", nullable=False)
     max_members: Mapped[int] = mapped_column(Integer, server_default="5", nullable=False)
     created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
     updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         onupdate=func.now(),
         nullable=False,
@@ -84,6 +86,7 @@ class OrgMember(Base):
     )
     role: Mapped[str] = mapped_column(String(20), server_default="viewer", nullable=False)
     joined_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
diff --git a/backend/app/models/platform_rule.py b/backend/app/models/platform_rule.py
index f68bdac..0e777f1 100644
--- a/backend/app/models/platform_rule.py
+++ b/backend/app/models/platform_rule.py
@@ -1,7 +1,7 @@
 import uuid
 from datetime import datetime
 
-from sqlalchemy import String, Boolean, ForeignKey, Index, func, Text
+from sqlalchemy import String, Boolean, ForeignKey, Index, func, Text, DateTime
 from sqlalchemy import Uuid
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
@@ -24,6 +24,7 @@ class PlatformRule(Base):
     severity: Mapped[str] = mapped_column(String(20), nullable=False)
     is_active: Mapped[bool] = mapped_column(Boolean, server_default="true", nullable=False)
     updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         onupdate=func.now(),
         nullable=False,
diff --git a/backend/app/models/platform_rule_version.py b/backend/app/models/platform_rule_version.py
index 425cd1d..445e7eb 100644
--- a/backend/app/models/platform_rule_version.py
+++ b/backend/app/models/platform_rule_version.py
@@ -1,7 +1,7 @@
 import uuid
 from datetime import datetime
 
-from sqlalchemy import String, Integer, Index, func
+from sqlalchemy import String, Integer, Index, func, DateTime
 from sqlalchemy import Uuid
 from sqlalchemy.orm import Mapped, mapped_column
 
@@ -22,7 +22,7 @@ class PlatformRuleVersion(Base):
     rule_data: Mapped[dict] = mapped_column(JSONType, nullable=False)
     change_summary: Mapped[str | None] = mapped_column(String(500), nullable=True)
     created_by: Mapped[str | None] = mapped_column(String(100), nullable=True)
-    created_at: Mapped[datetime] = mapped_column(server_default=func.now())
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())
 
     __table_args__ = (
         Index("idx_rule_versions_rule_id", "rule_id"),
diff --git a/backend/app/models/schema_suggestion.py b/backend/app/models/schema_suggestion.py
index 57bebff..68aad0d 100644
--- a/backend/app/models/schema_suggestion.py
+++ b/backend/app/models/schema_suggestion.py
@@ -52,10 +52,12 @@ class SchemaSuggestion(Base):
         JSONType, nullable=True,
     )
     created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         nullable=False,
     )
     updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
         server_default=func.now(),
         onupdate=func.now(),
         nullable=False,