fix: add global exception handler to log 500 errors

- Added @app.exception_handler(Exception) that logs full traceback via
  logger.exception() into superset_tools_app logger (visible in docker logs)
- Previously FastAPI/Starlette wrote unhandled exceptions to uvicorn.error
  logger, making 500 errors invisible in docker logs
- Added JSONResponse import for the handler

backend/src/app.py

@@ -21,7 +21,7 @@ project_root = Path(__file__).resolve().parent.parent.parent
 from alembic.config import Config as AlembicConfig
 from fastapi import FastAPI, HTTPException, Request, WebSocket, WebSocketDisconnect
 from fastapi.middleware.cors import CORSMiddleware
-from fastapi.responses import FileResponse
+from fastapi.responses import FileResponse, JSONResponse
 from fastapi.staticfiles import StaticFiles
 from starlette.middleware.base import BaseHTTPMiddleware
 from starlette.middleware.sessions import SessionMiddleware
@@ -237,6 +237,26 @@ class HSTSMiddleware(BaseHTTPMiddleware):
 
 app.add_middleware(HSTSMiddleware)
 # #endregion app_middleware
+# #region global_exception_handler [C:2] [TYPE Function]
+# @BRIEF Global exception handler — logs all unhandled 500 errors into the app logger.
+# @PRE request is a FastAPI Request object.
+# @POST Logs full traceback to superset_tools_app logger; returns 500.
+# @RATIONALE FastAPI/Starlette writes unhandled exceptions to uvicorn.error logger,
+#           which is not captured in docker logs. This handler ensures every 500
+#           appears in our structured JSON log output.
+@app.exception_handler(Exception)
+async def global_exception_handler(request: Request, exc: Exception):
+    logger.exception(
+        f"Unhandled exception: {request.method} {request.url.path}",
+        extra={"src": "app.exception_handler", "path": request.url.path, "method": request.method},
+    )
+    return JSONResponse(
+        status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+        content={"detail": "Internal server error", "path": request.url.path},
+    )
+# #endregion global_exception_handler
+
+
 # #region network_error_handler [C:1] [TYPE Function]
 # @BRIEF Global exception handler for NetworkError.
 # @PRE request is a FastAPI Request object.