Refactor: fix type errors in remote parser and signals

- remote.py: add `if TYPE_CHECKING: assert` guards before the Azure
  client construction to narrow config.endpoint and config.api_key from
  str|None to str. The narrowing is safe: engine_is_valid() guarantees
  both are non-None when it returns True (api_key explicitly; endpoint
  via `not (engine=="azureai" and endpoint is None)` for the only valid
  engine). Asserts are wrapped in TYPE_CHECKING so they carry zero
  runtime cost.

- signals.py: add full type annotations — return types, Any-typed
  sender parameter, and explicit logging_group argument replacing *args.
  Add `from __future__ import annotations` for consistent annotation style.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/paperless/parsers/remote.py

@@ -377,6 +377,13 @@ class RemoteDocumentParser:
         str | None
             Extracted text, or None if the Azure call failed.
         """
+        if TYPE_CHECKING:
+            # Callers must have already validated config via engine_is_valid():
+            # engine_is_valid() asserts api_key is not None and (for azureai)
+            # endpoint is not None, so these casts are provably safe.
+            assert config.endpoint is not None
+            assert config.api_key is not None
+
         from azure.ai.documentintelligence import DocumentIntelligenceClient
         from azure.ai.documentintelligence.models import AnalyzeDocumentRequest
         from azure.ai.documentintelligence.models import AnalyzeOutputOption

src/paperless_remote/signals.py

@@ -1,10 +1,15 @@
-def get_parser(*args, **kwargs):
+from __future__ import annotations
+
+from typing import Any
+
+
+def get_parser(logging_group: object = None) -> Any:
     from paperless.parsers.remote import RemoteDocumentParser
 
-    return RemoteDocumentParser(*args, **kwargs)
+    return RemoteDocumentParser(logging_group)
 
 
-def get_supported_mime_types():
+def get_supported_mime_types() -> dict[str, str]:
     from django.conf import settings
 
     from paperless.parsers.remote import RemoteDocumentParser
@@ -20,7 +25,7 @@ def get_supported_mime_types():
     return RemoteDocumentParser.supported_mime_types()
 
 
-def remote_consumer_declaration(sender, **kwargs):
+def remote_consumer_declaration(sender: Any, **kwargs: Any) -> dict[str, Any]:
     return {
         "parser": get_parser,
         "weight": 5,