cleanup all worker stats when starting up servers

server/metrics/MemoryMetricsStore.py

@@ -8,5 +8,11 @@ class MemoryMetricsStore:
   async def load_all(self) -> list[dict]:
     return [dict(value) for value in self._snapshots.values()]
 
+  async def clear_all(self) -> None:
+    self._snapshots.clear()
+
+  async def acquire_startup_cleanup_lock(self, lock_key:str, ttl_seconds:int=300) -> bool:
+    return True
+
   async def close(self) -> None:
     return None