Remove 1000-result limit, add Redis caching and virtual scrolling

- Remove hard-coded limit=1000 default from listing_geojson and streaming
  endpoints, allowing all matching results to be returned
- Add Redis caching service (db=2, 30min TTL) that caches query results
  as Redis Lists for fast re-queries with reduced DB load
- Integrate cache into streaming endpoint: serve from cache on hit,
  populate cache on miss during DB streaming
- Invalidate cache after scrape completes (both success and no-new-listings)
- Replace ScrollArea with react-virtuoso in ListView for virtual scrolling,
  keeping only ~20-30 DOM nodes regardless of list size
- Handle metadata streaming message to show "0 / N" progress from start
- Throttle frontend state updates with requestAnimationFrame to prevent
  UI jank from rapid re-renders during cached response streaming

crawler/frontend/src/App.tsx

@@ -67,16 +67,32 @@ function App() {
     setStreamingProgress({ count: 0 });
     setListingData(null);
 
+    let updateScheduled = false;
+
+    const flushUpdate = () => {
+      updateScheduled = false;
+      setListingData({
+        type: 'FeatureCollection',
+        features: [...accumulatedFeaturesRef.current]
+      });
+    };
+
+    const scheduleUpdate = () => {
+      if (!updateScheduled) {
+        updateScheduled = true;
+        requestAnimationFrame(flushUpdate);
+      }
+    };
+
     try {
       for await (const batch of streamListingGeoJSON(user, parameters, (progress) => {
         setStreamingProgress(progress);
       })) {
         accumulatedFeaturesRef.current.push(...batch);
-        setListingData({
-          type: 'FeatureCollection',
-          features: [...accumulatedFeaturesRef.current]
-        });
+        scheduleUpdate();
       }
+      // Final flush to ensure all data is rendered
+      flushUpdate();
     } catch (error) {
       if (error instanceof Error) {
         setSubmitError(error.message);