feat: add MCP tool integration

backend/db/models.py

@@ -207,15 +207,55 @@ class AssistantModelBinding(Base):
     )
 
 
+class McpServer(Base):
+    """Workspace-level remote MCP connection used to discover executable tools."""
+
+    __tablename__ = "mcp_servers"
+
+    id: Mapped[str] = mapped_column(String(40), primary_key=True)
+    name: Mapped[str] = mapped_column(String(128))
+    description: Mapped[str] = mapped_column(String(2048), default="")
+    transport: Mapped[str] = mapped_column(String(32), default="streamable_http")
+    url: Mapped[str] = mapped_column(String(2048))
+    config: Mapped[dict] = mapped_column(JSONB, default=dict)
+    secrets: Mapped[dict] = mapped_column(JSONB, default=dict)
+    status: Mapped[str] = mapped_column(String(16), index=True, default="active")
+    last_synced_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()
+    )
+
+
 class Tool(Base):
     """Reusable LLM tool definition; supported types are executed at runtime."""
 
     __tablename__ = "tools"
+    __table_args__ = (
+        UniqueConstraint(
+            "mcp_server_id",
+            "remote_tool_name",
+            name="uq_tools_mcp_server_remote_name",
+        ),
+    )
 
     id: Mapped[str] = mapped_column(String(40), primary_key=True)
     name: Mapped[str] = mapped_column(String(128))
     function_name: Mapped[str] = mapped_column(String(64), unique=True, index=True)
     type: Mapped[str] = mapped_column(String(24), index=True)
+    mcp_server_id: Mapped[str | None] = mapped_column(
+        String(40),
+        ForeignKey("mcp_servers.id", ondelete="CASCADE"),
+        nullable=True,
+        index=True,
+    )
+    remote_tool_name: Mapped[str | None] = mapped_column(
+        String(255), nullable=True
+    )
     description: Mapped[str] = mapped_column(String(2048), default="")
     definition: Mapped[dict] = mapped_column(JSONB, default=dict)
     secrets: Mapped[dict] = mapped_column(JSONB, default=dict)