fix(billing): auto-detect repo root for shared module import in local dev

services/billing/app/main.py

@@ -11,9 +11,16 @@ The webhook endpoint is exposed WITHOUT ForwardAuth so Stripe can reach it.
 from __future__ import annotations
 
 import logging
+import sys
 from contextlib import asynccontextmanager
+from pathlib import Path
 from typing import AsyncGenerator
 
+# Ensure the repo root is on sys.path so "shared" is importable in local dev.
+_repo_root = str(Path(__file__).resolve().parents[3])
+if _repo_root not in sys.path:
+    sys.path.insert(0, _repo_root)
+
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware