feat(metadata): add rate limit retry support to metadata providers

Add RateLimitRetryingProvider and _RateLimitRetryHelper classes to handle rate limiting with exponential backoff retries. Update get_metadata_provider function to automatically wrap providers with rate limit handling. This improves reliability when external APIs return rate limit errors by implementing automatic retries with configurable delays and jitter.

tests/services/test_metadata_service.py

@@ -0,0 +1,62 @@
+from types import SimpleNamespace
+from unittest.mock import AsyncMock
+
+import pytest
+
+from py.services import metadata_service
+from py.services.model_metadata_provider import (
+    FallbackMetadataProvider,
+    ModelMetadataProvider,
+    RateLimitRetryingProvider,
+)
+
+
+class DummyProvider(ModelMetadataProvider):
+    async def get_model_by_hash(self, model_hash: str):
+        return None, None
+
+    async def get_model_versions(self, model_id: str):
+        return None
+
+    async def get_model_versions_bulk(self, model_ids):
+        return None
+
+    async def get_model_version(self, model_id: int = None, version_id: int = None):
+        return None
+
+    async def get_model_version_info(self, version_id: str):
+        return None, None
+
+    async def get_user_models(self, username: str):
+        return None
+
+
+@pytest.mark.asyncio
+async def test_get_metadata_provider_wraps_non_fallback(monkeypatch):
+    provider = DummyProvider()
+    dummy_manager = SimpleNamespace(_get_provider=lambda _name=None: provider)
+    monkeypatch.setattr(
+        metadata_service.ModelMetadataProviderManager,
+        "get_instance",
+        AsyncMock(return_value=dummy_manager),
+    )
+
+    wrapped = await metadata_service.get_metadata_provider("dummy")
+
+    assert isinstance(wrapped, RateLimitRetryingProvider)
+    assert wrapped is not provider
+
+
+@pytest.mark.asyncio
+async def test_get_metadata_provider_returns_fallback_as_is(monkeypatch):
+    fallback = FallbackMetadataProvider([("dummy", DummyProvider())])
+    dummy_manager = SimpleNamespace(_get_provider=lambda _name=None: fallback)
+    monkeypatch.setattr(
+        metadata_service.ModelMetadataProviderManager,
+        "get_instance",
+        AsyncMock(return_value=dummy_manager),
+    )
+
+    provider = await metadata_service.get_metadata_provider()
+
+    assert provider is fallback