Fix HF token detection: explicitly read HF_TOKEN from os.environ

HfApi() auto-detection was failing in the Space's Python 3.13 runtime,
causing persistence to always be disabled. Now explicitly passes the
token from os.environ.get("HF_TOKEN") to HfApi(token=...).

app.py

@@ -190,11 +190,14 @@ def _init_persistence() -> bool:
     global _scheduler
     _DATA_DIR.mkdir(parents=True, exist_ok=True)
 
-    api = HfApi()
-    if not api.token:
-        logger.warning("No HF token found — data persistence disabled")
+    token = os.environ.get("HF_TOKEN")
+    if not token:
+        logger.warning("No HF token found — data persistence disabled (HF_TOKEN not in env)")
         return False
 
+    logger.info("HF_TOKEN found, initializing persistence...")
+    api = HfApi(token=token)
+
     try:
         # Download existing data files from the repo before starting the scheduler
         for filename in ["submissions.jsonl", "key_requests.jsonl", "admin_audit.jsonl"]: