fix: resolve all 64 mypy errors across backend

- Add dict[str, Any] / list[Any] type params throughout (fingerprint, models, schemas, scanner, status_checker)
- Add return type annotations to all route functions (nodes, edges, canvas, scan, auth, status, main)
- Fix no-any-return in security.py: cast pwd/jwt results to bool/str explicitly
- Fix canvas.py: use model_validate() for NodeResponse/EdgeResponse, rename db_node/db_edge upsert vars
- Fix scheduler.py: rename 'result' → 'check_result' to avoid type collision
- Fix get_db() return type: AsyncGenerator[AsyncSession, None]
- Add types-PyYAML for yaml import stubs
- Fix scanner.py: remove unnecessary type: ignore comment (nmap has stubs)
- Fix scan.py: wrap scalars().all() with list() for Sequence→list compatibility

backend/app/schemas/nodes.py

@@ -20,7 +20,7 @@ class NodeBase(BaseModel):
     pos_y: float = 0
     parent_id: str | None = None
     container_mode: bool = False
-    custom_colors: dict | None = None
+    custom_colors: dict[str, Any] | None = None
 
 
 class NodeCreate(NodeBase):
@@ -42,7 +42,7 @@ class NodeUpdate(BaseModel):
     pos_x: float | None = None
     pos_y: float | None = None
     container_mode: bool | None = None
-    custom_colors: dict | None = None
+    custom_colors: dict[str, Any] | None = None
 
 
 class NodeResponse(NodeBase):