feat(notify): 站内通知补齐完成、到期逾期与知识事件

backend/app/models_ticket.py

@@ -26,6 +26,7 @@ from sqlalchemy import (
     Text,
     UniqueConstraint,
     func,
+    text,
 )
 from sqlalchemy.dialects.postgresql import UUID as PgUUID
 from sqlalchemy.orm import Mapped, mapped_column
@@ -121,6 +122,16 @@ class Notification(Base, Timestamps):
     __table_args__ = (
         Index("ix_notification_ws_user_read", "workspace_id", "user_id", "read_at"),
         Index("ix_notification_ws_created", "workspace_id", "created_at"),
+        # 到期/逾期提醒由后台循环生成，可能被重复触发；带 dedupe_key 的写入用
+        # ON CONFLICT DO NOTHING，把"同一件事只提醒一次"交给数据库保证。
+        Index(
+            "uq_notification_dedupe",
+            "workspace_id",
+            "user_id",
+            "dedupe_key",
+            unique=True,
+            postgresql_where=text("dedupe_key IS NOT NULL"),
+        ),
     )
 
     id: Mapped[uuid.UUID] = mapped_column(PgUUID(as_uuid=True), primary_key=True, default=new_uuid)
@@ -137,6 +148,9 @@ class Notification(Base, Timestamps):
     title: Mapped[str] = mapped_column(String(120), nullable=False)
     body: Mapped[str] = mapped_column(String(300), nullable=False, default="")
     read_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
+    # 提醒类通知的幂等键（如 task_due_soon:<item>:<due_at>）。
+    # 普通通知为空，不参与唯一约束。
+    dedupe_key: Mapped[str | None] = mapped_column(String(120))
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now()
     )