cleanup all worker stats when starting up servers

tests/test_MetricsManager.py

@@ -1,4 +1,5 @@
 import unittest
+from typing import Any, cast
 
 from server.metrics.MetricsManager import MetricsManager
 
@@ -139,5 +140,26 @@ class TestMetricsManager(unittest.IsolatedAsyncioTestCase):
     self.assertEqual(merged["metrics_backend"], "redis")
     await manager.close()
 
+  async def test_acquire_startup_cleanup_lock_uses_store_for_redis_backend(self):
+    class FakeStore:
+      def __init__(self):
+        self.calls = []
+
+      async def acquire_startup_cleanup_lock(self, lock_key:str, ttl_seconds:int=300):
+        self.calls.append((lock_key, ttl_seconds))
+        return True
+
+      async def close(self):
+        return None
+
+    manager = MetricsManager(backend="redis", key_prefix="snake:metrics:worker")
+    fake_store = FakeStore()
+    manager.store = cast(Any, fake_store)
+
+    allowed = await manager.acquire_startup_cleanup_lock(180)
+    self.assertTrue(allowed)
+    self.assertEqual(fake_store.calls, [("snake:metrics:worker:startup_cleanup_lock", 180)])
+    await manager.close()
+
 if __name__ == "__main__":
   unittest.main()