Typing fixes

I used several ignores that I am surprised I needed - MyPy is not
behaving quite as I expected.

Author: rwb27

src/labthings_fastapi/outputs/blob.py

@@ -70,6 +70,8 @@ def open(self) -> io.IOBase: ...
 class ServerSideBlobData(BlobData, Protocol):
     """A BlobOutput protocol for server-side use, i.e. including `response()`"""
 
+    id: Optional[uuid.UUID] = None
+
     def response(self) -> Response: ...
 
 
@@ -171,7 +173,8 @@ def to_dict(self) -> Mapping[str, str]:
         if self.href == "blob://local":
             try:
                 blobdata_to_url = blobdata_to_url_ctx.get()
-                href = blobdata_to_url(self.data)
+                # MyPy seems to miss that `self.data` is a property, hence the ignore
+                href = blobdata_to_url(self.data)  # type: ignore[arg-type]
             except LookupError:
                 raise LookupError(
                     "Blobs may only be serialised inside the "
@@ -224,7 +227,7 @@ def open(self) -> io.IOBase:
     @classmethod
     def from_bytes(cls, data: bytes) -> Self:
         """Create a BlobOutput from a bytes object"""
-        return cls.model_construct(
+        return cls.model_construct(  # type: ignore[return-value]
             href="blob://local",
             _data=BlobBytes(data, media_type=cls.default_media_type()),
         )
@@ -238,7 +241,7 @@ def from_temporary_directory(cls, folder: TemporaryDirectory, file: str) -> Self
         collected.
         """
         file_path = os.path.join(folder.name, file)
-        return cls.model_construct(
+        return cls.model_construct(  # type: ignore[return-value]
             href="blob://local",
             _data=BlobFile(
                 file_path,
@@ -257,7 +260,7 @@ def from_file(cls, file: str) -> Self:
         temporary. If you are using temporary files, consider creating your
         Blob with `from_temporary_directory` instead.
         """
-        return cls.model_construct(
+        return cls.model_construct(  # type: ignore[return-value]
             href="blob://local",
             _data=BlobFile(file, media_type=cls.default_media_type()),
         )
@@ -326,7 +329,7 @@ def attach_to_app(self, app: FastAPI):
 async def blob_serialisation_context_manager(request: Request):
     """Set context variables to allow blobs to be serialised"""
     thing_server = find_thing_server(request.app)
-    blob_manager = thing_server.blob_data_manager
+    blob_manager: BlobDataManager = thing_server.blob_data_manager
     url_for = request.url_for
 
     def blobdata_to_url(blob: ServerSideBlobData) -> str:

src/labthings_fastapi/server/__init__.py

@@ -38,6 +38,7 @@ def __init__(self, settings_folder: Optional[str] = None):
 
     app: FastAPI
     action_manager: ActionManager
+    blob_data_manager: BlobDataManager
 
     def set_cors_middleware(self) -> None:
         self.app.add_middleware(