feat(filter): add debounced tag search with backend search-tags endpoint

tests/routes/test_model_query_handler.py

@@ -36,3 +36,53 @@ async def test_model_query_handler_rejects_negative_limit_for_base_models():
     await handler.get_base_models(SimpleNamespace(query={"limit": "-1"}))
 
     assert service.received_limit == 20
+
+
+class DummySearchTagsService:
+    """Minimal service stub recording search_tags arguments."""
+
+    def __init__(self, result=None):
+        self.received_query = None
+        self.received_limit = None
+        self._result = result or []
+
+    async def search_tags(self, query, limit):
+        self.received_query = query
+        self.received_limit = limit
+        return self._result
+
+
+@pytest.mark.asyncio
+async def test_model_query_handler_search_tags_passes_query_and_limit():
+    service = DummySearchTagsService(result=[{"tag": "anime", "count": 3}])
+    handler = ModelQueryHandler(service=service, logger=logging.getLogger(__name__))
+
+    response = await handler.search_tags(
+        SimpleNamespace(query={"q": "ani", "limit": "50"})
+    )
+    payload = json.loads(response.text)
+
+    assert payload["success"] is True
+    assert payload["tags"] == [{"tag": "anime", "count": 3}]
+    assert service.received_query == "ani"
+    assert service.received_limit == 50
+
+
+@pytest.mark.asyncio
+async def test_model_query_handler_search_tags_defaults_limit_to_20():
+    service = DummySearchTagsService()
+    handler = ModelQueryHandler(service=service, logger=logging.getLogger(__name__))
+
+    await handler.search_tags(SimpleNamespace(query={}))
+
+    assert service.received_limit == 20
+
+
+@pytest.mark.asyncio
+async def test_model_query_handler_search_tags_clamps_negative_limit():
+    service = DummySearchTagsService()
+    handler = ModelQueryHandler(service=service, logger=logging.getLogger(__name__))
+
+    await handler.search_tags(SimpleNamespace(query={"limit": "-5"}))
+
+    assert service.received_limit == 20