fix: 422 errors on all plugin routes — wrapper(*args, **kwargs) was interpreted as query params by FastAPI

The wrap_plugin_route wrapper had *args, **kwargs as parameters.
FastAPI interpreted these as required query parameters 'args' and 'kwargs',
causing 422 Unprocessable Entity on EVERY plugin route (mail, calendar, dms, reports, etc.).

Fix: Use functools.wraps(handler) to copy the original signature,
then remove __annotations__ (to avoid ForwardRef('UploadFile') issues),
and manually set __signature__ from the original handler.

app/core/plugin_error_handler.py

@@ -1,6 +1,7 @@
 """Plugin error isolation wrapper."""
 import logging
 import functools
+import inspect
 from fastapi import UploadFile as _UploadFile  # noqa: F401 — needed for ForwardRef resolution
 from fastapi.responses import JSONResponse
 
@@ -10,10 +11,11 @@ logger = logging.getLogger(__name__)
 def wrap_plugin_route(handler):
     """Decorator that isolates plugin route errors and returns structured JSON.
 
-    Does NOT use functools.wraps to avoid copying __annotations__ and
-    __wrapped__ — FastAPI would otherwise try to resolve
-    ``ForwardRef('UploadFile')`` from the original handler's signature.
+    Copies the original handler's signature so FastAPI sees the correct
+    parameters (path params, query params, body, etc.) instead of *args/**kwargs.
+    Avoids copying __annotations__ to prevent ForwardRef('UploadFile') issues.
     """
+    @functools.wraps(handler)
     async def wrapper(*args, **kwargs):
         try:
             return await handler(*args, **kwargs)
@@ -23,8 +25,16 @@ def wrap_plugin_route(handler):
                 status_code=500,
                 content={'detail': f'Plugin error: {exc}', 'code': 'plugin_error'}
             )
-    # Preserve identity for debugging but NOT __wrapped__ or __annotations__
-    wrapper.__name__ = getattr(handler, '__name__', 'wrapper')
-    wrapper.__module__ = getattr(handler, '__module__', __name__)
-    wrapper.__qualname__ = getattr(handler, '__qualname__', 'wrapper')
+    # Remove annotations that cause ForwardRef resolution issues
+    wrapper.__annotations__ = {}
+    # Remove __wrapped__ so FastAPI doesn't try to resolve the original signature
+    # (which may have ForwardRef('UploadFile') that can't be resolved)
+    if hasattr(wrapper, '__wrapped__'):
+        delattr(wrapper, '__wrapped__')
+    # Copy the signature from the original handler so FastAPI sees correct params
+    try:
+        orig_sig = inspect.signature(handler)
+        wrapper.__signature__ = orig_sig
+    except (ValueError, TypeError):
+        pass
     return wrapper