fix: Add cache control headers and improve typing indicator

- Add proper cache control headers in static.ts
- HTML files: no-cache to always get fresh version
- Assets: long cache with immutable (content-hashed filenames)
- Improve typing indicator animation (larger dots, faster animation)

server/static.ts

@@ -22,11 +22,24 @@ export function serveStatic(app: Express) {
     );
   }
 
-  // Serve static files from the public directory (includes attached_assets)
-  app.use(express.static(distPath));
+  // Serve static assets with long cache (they have content hashes in filenames)
+  app.use("/assets", express.static(path.join(distPath, "assets"), {
+    maxAge: '1y',
+    immutable: true
+  }));
 
-  // fall through to index.html if the file doesn't exist
+  // Serve other static files with no-cache for HTML
+  app.use(express.static(distPath, {
+    setHeaders: (res, filePath) => {
+      if (filePath.endsWith('.html')) {
+        res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
+      }
+    }
+  }));
+
+  // fall through to index.html if the file doesn't exist (with no-cache)
   app.use("*", (_req, res) => {
+    res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
     res.sendFile(path.resolve(distPath, "index.html"));
   });
 }