1. plugin_error_handler.py: Remove return_annotation from copied signature
to prevent FastAPI ForwardRef('UploadFile') resolution failure on routes
with file upload endpoints (dms, calendar, mail, kommunikation, ai_assistant)
2. middleware.py: Skip CSRF check for WebSocket upgrade requests
WebSocket connections use GET with upgrade header — should not be
blocked by CSRF middleware
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.
Agent Zero