fix: remove wrap_plugin_route — it broke ForwardRef resolution for body params

wrap_plugin_route copied __signature__ from the original handler but
the wrapper's __globals__ namespace (plugin_error_handler.py) did not
contain the Pydantic models (ConversationCreate, MessageCreate, etc.).
FastAPI could not resolve ForwardRef('ConversationCreate') → 422 on
all POST routes with body parameters.

Removing the wrapper entirely fixes this. Plugin error isolation can
be re-added later using a different approach (middleware or exception handler).

app/main.py

@@ -435,17 +435,12 @@ def create_app() -> FastAPI:
                         try:
                             router_module = importlib.import_module(route_def.module)
                             router = getattr(router_module, route_def.router_attr)
-                            # Wrap each HTTP route handler with plugin error isolation
-                            # and add active-plugin check per-route (not router-level)
-                            # so WebSocket routes are NOT affected.
+                            # Skip WebSocket routes — no wrapping, no plugin check
                             from starlette.routing import WebSocketRoute
-                            from fastapi import APIRouter as _AR
                             plugin_dep = Depends(require_active_plugin(plugin_name))
                             for route in router.routes:
                                 if isinstance(route, WebSocketRoute):
-                                    continue  # WebSocket: no wrap, no plugin check
-                                if hasattr(route, 'endpoint'):
-                                    route.endpoint = wrap_plugin_route(route.endpoint)
+                                    continue
                                 # Add require_active_plugin to each HTTP route's dependencies
                                 if not hasattr(route, 'dependencies'):
                                     route.dependencies = []