fix(entrypoint): always bind uvicorn to 7860 (HF Spaces proxy port)

The PORT secret is 8000, so uvicorn bound 8000 and the platform never
saw the app come up -> stuck APP_STARTING. Spaces always route to 7860.

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

entrypoint.py

@@ -169,7 +169,10 @@ def main():
     if not broker_url:
         print("[ENTRYPOINT] WARNING: no Redis reachable - bulk jobs use the synchronous fallback", flush=True)
 
-    port = os.environ.get("PORT", "7860")
+    # Hugging Face Spaces always proxies to container port 7860; a PORT
+    # env/secret with another value (e.g. 8000) must not steer uvicorn,
+    # or the platform never sees the app start.
+    port = "7860"
 
     def spawn(kind):
         if kind == "worker":