Implement webhook

backend/db/models.py

@@ -374,3 +374,51 @@ class ConversationArtifact(Base):
         DateTime(timezone=True), server_default=func.now()
     )
     extra: Mapped[dict] = mapped_column(JSONB, default=dict)
+
+
+class SiteSetting(Base):
+    """Deployment-wide settings, split into public values and write-only secrets."""
+
+    __tablename__ = "site_settings"
+
+    key: Mapped[str] = mapped_column(String(64), primary_key=True)
+    value: Mapped[dict] = mapped_column(JSONB, default=dict)
+    secrets: Mapped[dict] = mapped_column(JSONB, default=dict)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), onupdate=func.now()
+    )
+
+
+class WebhookDelivery(Base):
+    """Immutable event snapshot plus its asynchronous delivery state."""
+
+    __tablename__ = "webhook_deliveries"
+
+    id: Mapped[str] = mapped_column(String(40), primary_key=True)
+    event_id: Mapped[str] = mapped_column(String(40), unique=True)
+    event_type: Mapped[str] = mapped_column(String(128), index=True)
+    conversation_id: Mapped[str | None] = mapped_column(
+        String(40),
+        ForeignKey("conversation_sessions.id", ondelete="SET NULL"),
+        nullable=True,
+        index=True,
+    )
+    payload: Mapped[dict] = mapped_column(JSONB)
+    url: Mapped[str] = mapped_column(String(2048))
+    secrets: Mapped[dict] = mapped_column(JSONB, default=dict)
+    status: Mapped[str] = mapped_column(String(16), index=True, default="pending")
+    attempt_count: Mapped[int] = mapped_column(Integer, default=0)
+    next_attempt_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True, index=True
+    )
+    last_status_code: Mapped[int | None] = mapped_column(Integer, nullable=True)
+    last_error: Mapped[str] = mapped_column(String(2048), default="")
+    delivered_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now()
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), onupdate=func.now()
+    )