fix: prevent infinite SSE reconnection after shutdown

Set realtime_flags to False in _close_sse_connection() to stop
the SSE listener thread from attempting reconnection after the
client has been shut down. Without this, the check on line 2304
would still pass even after shutdown since realtime_flags remained True.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: gustavohstrassburger

posthog/client.py

@@ -2351,10 +2351,13 @@ def sse_listener():
 
     def _close_sse_connection(self):
         """
-        Close the active SSE connection.
+        Close the active SSE connection and prevent reconnection.
         """
         if self.sse_connection:
             self.log.debug("[FEATURE FLAGS] Closing SSE connection")
+            # Disable realtime flags to prevent reconnection
+            self.realtime_flags = False
+
             with self._sse_lock:
                 self.sse_connected = False