feat: add model version management endpoints

- Add set_version_update_ignore endpoint to toggle ignore status for specific versions
- Add get_model_versions endpoint to retrieve version details with optional refresh
- Update serialization to include version-specific data and preview overrides
- Modify database schema to support version-level ignore tracking
- Improve error handling for rate limiting and missing models

These changes enable granular control over version updates and provide better visibility into model version status.

tests/routes/test_model_update_handler.py

@@ -0,0 +1,57 @@
+import logging
+from types import SimpleNamespace
+
+import pytest
+
+from py.config import config
+from py.routes.handlers.model_handlers import ModelUpdateHandler
+from py.services.model_update_service import ModelUpdateRecord, ModelVersionRecord
+
+
+class DummyScanner:
+    def __init__(self, cache):
+        self._cache = cache
+
+    async def get_cached_data(self):
+        return self._cache
+
+
+class DummyService:
+    def __init__(self, cache):
+        self.model_type = "lora"
+        self.scanner = DummyScanner(cache)
+
+
+@pytest.mark.asyncio
+async def test_build_preview_overrides_uses_static_urls():
+    cache = SimpleNamespace(version_index={123: {"preview_url": "/tmp/previews/example.png"}})
+    service = DummyService(cache)
+    handler = ModelUpdateHandler(
+        service=service,
+        update_service=SimpleNamespace(),
+        metadata_provider_selector=lambda *_: None,
+        logger=logging.getLogger(__name__),
+    )
+
+    record = ModelUpdateRecord(
+        model_type="lora",
+        model_id=42,
+        versions=[
+            ModelVersionRecord(
+                version_id=123,
+                name=None,
+                base_model=None,
+                released_at=None,
+                size_bytes=None,
+                preview_url=None,
+                is_in_library=True,
+                should_ignore=False,
+            )
+        ],
+        last_checked_at=None,
+        should_ignore_model=False,
+    )
+
+    overrides = await handler._build_preview_overrides(record)
+    expected = config.get_preview_static_url("/tmp/previews/example.png")
+    assert overrides == {123: expected}