Add temporary diagnostic wrapper to send_connection_request

Exposes actual exception type and message in 500 response detail
to identify the unhandled error. Will be removed after diagnosis.

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

backend/app/routers/connections.py

@@ -131,6 +131,16 @@ async def send_connection_request(
     current_user: User = Depends(get_current_user),
 ):
     """Send a connection request to another user."""
+    try:
+        return await _send_request_impl(body, request, background_tasks, db, current_user)
+    except HTTPException:
+        raise
+    except Exception as exc:
+        logger.error("send_connection_request UNHANDLED: %s", exc, exc_info=True)
+        raise HTTPException(status_code=500, detail=f"DEBUG: {type(exc).__name__}: {exc}")
+
+
+async def _send_request_impl(body, request, background_tasks, db, current_user):
     # Resolve target
     result = await db.execute(
         select(User).where(User.umbral_name == body.umbral_name)