fix: don't crash on missing GOOGLE_API_KEY at startup

Warn instead of raising RuntimeError so HF Space can boot
and show the UI. The key is set via HF Space secrets.

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

backend/main.py

@@ -21,10 +21,11 @@ from urgency import load_model
 
 load_dotenv()
 
-# Fail fast if Gemini API key is missing
+# Warn if Gemini API key is missing (don't crash — HF Spaces sets secrets as env vars)
 api_key = os.getenv("GOOGLE_API_KEY")
 if not api_key or api_key == "your_key_here":
-    raise RuntimeError("GOOGLE_API_KEY not set. Check backend/.env")
+    import warnings
+    warnings.warn("GOOGLE_API_KEY not set. Add it as a Secret in HuggingFace Space settings.")
 
 FRONTEND_URL = os.getenv("FRONTEND_URL", "http://localhost:5173")