Add comprehensive test suite: 219 new tests across backend and frontend

Backend (103 tests):
- Unit tests for listing_service, export_service, district_service
- Regression tests for API response contracts and query parameter validation
- Integration tests for API workflows, Redis listing cache, listing processor pipeline, and repository advanced queries
- E2E tests for streaming with filters, batching, caching, and task management

Frontend (116 tests):
- Service tests for apiClient, streamingService, taskService, listingService, healthService
- Hook tests for useTaskProgress (WebSocket + polling)
- Component tests for PropertyCard, FilterPanel, Header, ListView, TaskProgressDrawer, TaskIndicator, StreamingProgressBar, HealthIndicator
- E2E tests for filter-stream-display flow

Infrastructure:
- Add pytest-xdist and test markers (regression, integration, e2e)
- Add conftest fixtures: fake_redis, rent_listing_factory, seeded_repository
- Add vitest + testing-library + MSW for frontend testing

tests/unit/test_listing_service.py

@@ -0,0 +1,129 @@
+"""Unit tests for services/listing_service.py."""
+
+import pytest
+from unittest.mock import AsyncMock, MagicMock, patch
+
+from models.listing import QueryParameters, ListingType
+from services import listing_service
+
+
+class TestGetListings:
+    async def test_empty_db_returns_zero(self, listing_repository):
+        result = await listing_service.get_listings(listing_repository)
+        assert result.total_count == 0
+        assert result.listings == []
+
+    async def test_with_results_returns_correct_count(self, listing_repository, sample_rent_listings):
+        await listing_repository.upsert_listings(sample_rent_listings)
+        result = await listing_service.get_listings(listing_repository)
+        assert result.total_count == len(sample_rent_listings)
+        assert len(result.listings) == len(sample_rent_listings)
+
+    async def test_with_query_parameters_filters(self, listing_repository, sample_rent_listings):
+        await listing_repository.upsert_listings(sample_rent_listings)
+        params = QueryParameters(listing_type=ListingType.RENT, min_bedrooms=3)
+        result = await listing_service.get_listings(listing_repository, query_parameters=params)
+        for listing in result.listings:
+            assert listing.number_of_bedrooms >= 3
+
+    async def test_limit_works(self, listing_repository, sample_rent_listings):
+        await listing_repository.upsert_listings(sample_rent_listings)
+        result = await listing_service.get_listings(listing_repository, limit=1)
+        assert len(result.listings) <= 1
+
+    async def test_only_ids_works(self, listing_repository, sample_rent_listings):
+        await listing_repository.upsert_listings(sample_rent_listings)
+        target_ids = [sample_rent_listings[0].id]
+        result = await listing_service.get_listings(listing_repository, only_ids=target_ids)
+        assert all(l.id in target_ids for l in result.listings)
+
+
+class TestRefreshListings:
+    async def test_async_mode_dispatches_celery_task(self, listing_repository):
+        params = QueryParameters(listing_type=ListingType.RENT)
+        with patch("tasks.listing_tasks.dump_listings_task") as mock_task:
+            mock_task.apply_async.return_value = MagicMock(id="fake-task-id")
+            result = await listing_service.refresh_listings(
+                listing_repository, params, async_mode=True, user_email="test@example.com"
+            )
+        mock_task.apply_async.assert_called_once()
+        assert result.task_id == "fake-task-id"
+
+    async def test_sync_mode_calls_fetcher(self, listing_repository):
+        params = QueryParameters(listing_type=ListingType.RENT)
+        with patch("services.listing_fetcher.dump_listings", new_callable=AsyncMock) as mock_dump:
+            mock_dump.return_value = []
+            result = await listing_service.refresh_listings(
+                listing_repository, params, async_mode=False
+            )
+        mock_dump.assert_called_once()
+        assert result.task_id is None
+
+    async def test_full_mode_calls_dump_listings_full(self, listing_repository):
+        params = QueryParameters(listing_type=ListingType.RENT)
+        with patch("services.listing_fetcher.dump_listings_full", new_callable=AsyncMock) as mock_full:
+            mock_full.return_value = []
+            result = await listing_service.refresh_listings(
+                listing_repository, params, full=True, async_mode=False
+            )
+        mock_full.assert_called_once()
+
+    async def test_sync_returns_new_listings_count(self, listing_repository):
+        params = QueryParameters(listing_type=ListingType.RENT)
+        fake_listings = [MagicMock(), MagicMock(), MagicMock()]
+        with patch("services.listing_fetcher.dump_listings", new_callable=AsyncMock) as mock_dump:
+            mock_dump.return_value = fake_listings
+            result = await listing_service.refresh_listings(
+                listing_repository, params, async_mode=False
+            )
+        assert result.new_listings_count == 3
+
+    async def test_async_result_has_message(self, listing_repository):
+        params = QueryParameters(listing_type=ListingType.RENT)
+        with patch("tasks.listing_tasks.dump_listings_task") as mock_task:
+            mock_task.apply_async.return_value = MagicMock(id="fake-task-id")
+            result = await listing_service.refresh_listings(
+                listing_repository, params, async_mode=True
+            )
+        assert result.message is not None
+        assert len(result.message) > 0
+
+
+class TestDownloadImages:
+    async def test_calls_image_fetcher(self, listing_repository):
+        with patch("services.image_fetcher.dump_images", new_callable=AsyncMock) as mock_dump:
+            mock_dump.return_value = None
+            result = await listing_service.download_images(listing_repository)
+        mock_dump.assert_called_once()
+
+
+class TestDetectFloorplans:
+    async def test_calls_floorplan_detector(self, listing_repository):
+        with patch("services.floorplan_detector.detect_floorplan", new_callable=AsyncMock) as mock_detect:
+            mock_detect.return_value = None
+            result = await listing_service.detect_floorplans(listing_repository)
+        mock_detect.assert_called_once()
+
+
+class TestCalculateRoutes:
+    async def test_passes_correct_travel_mode(self, listing_repository):
+        with patch("services.route_calculator.calculate_route", new_callable=AsyncMock) as mock_calc:
+            mock_calc.return_value = None
+            result = await listing_service.calculate_routes(
+                listing_repository,
+                destination_address="London Bridge",
+                travel_mode="TRANSIT",
+                limit=10,
+            )
+        mock_calc.assert_called_once()
+
+    async def test_passes_limit(self, listing_repository):
+        with patch("services.route_calculator.calculate_route", new_callable=AsyncMock) as mock_calc:
+            mock_calc.return_value = None
+            result = await listing_service.calculate_routes(
+                listing_repository,
+                destination_address="Kings Cross",
+                travel_mode="TRANSIT",
+                limit=5,
+            )
+        assert result == 5