Format mesh_coordinator.py with Black

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: alicup29

sleap_rtc/worker/mesh_coordinator.py

@@ -857,7 +857,9 @@ def _prune_e2e_sessions(self):
             del self._e2e_sessions[sid]
             logger.debug(f"[E2E] Pruned expired session {sid[:8]}...")
 
-    def _decrypt_if_encrypted(self, data: Dict[str, Any]) -> tuple[Dict[str, Any], str | None]:
+    def _decrypt_if_encrypted(
+        self, data: Dict[str, Any]
+    ) -> tuple[Dict[str, Any], str | None]:
         """If the message is an encrypted relay envelope, decrypt it.
 
         Returns: