fix: cache Neo4j driver failure state to avoid 60s retry on every request

get_global_driver() now sets _driver_unavailable=True when the initial
connection fails, so subsequent calls fail immediately instead of
spending 60s retrying each time. Added reset_global_driver() to allow
manual reconnection after Neo4j comes back up.

Also fixes APP_BOLT_URL in .env: was bolt://bolt.classroomcopilot.ai
(public IP, port not exposed), now bolt://192.168.0.209:7687 (LAN).

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

modules/database/tools/neo4j_driver_tools.py

@@ -127,16 +127,39 @@ def close_driver(driver: Optional[Driver]) -> None:
         logger.info("Closing driver")
         driver.close()
 
-# Global driver instance
+# Global driver instance — None means not yet initialised, _driver_unavailable=True means connection failed
 _driver: Optional[Driver] = None
+_driver_unavailable: bool = False
 
 def get_global_driver() -> Optional[Driver]:
-    """Get or create the global Neo4j driver instance."""
-    global _driver
+    """Get or create the global Neo4j driver instance.
+
+    Caches both success and failure so a broken Neo4j connection causes
+    a single 60-second retry at startup, then fast-fails on every
+    subsequent call instead of hanging for 60s each time.
+    """
+    global _driver, _driver_unavailable
+    if _driver_unavailable:
+        return None
     if _driver is None:
         _driver = get_driver()
+        if _driver is None:
+            _driver_unavailable = True
+            logger.error("Neo4j driver unavailable — all subsequent Neo4j calls will fail fast until process restarts")
     return _driver
 
+def reset_global_driver() -> None:
+    """Reset the cached driver, forcing a reconnection attempt on the next call.
+
+    Call this if Neo4j becomes available after the process started.
+    """
+    global _driver, _driver_unavailable
+    if _driver:
+        close_driver(_driver)
+    _driver = None
+    _driver_unavailable = False
+    logger.info("Global Neo4j driver reset — will reconnect on next request")
+
 @contextmanager
 def get_session(database: Optional[str] = None) -> Generator[Session, None, None]:
     """Get a Neo4j session using the global driver."""