Update favicon to new logo (#19)

## Summary
- Closes #18
- Replace stale `favicon.jpg` / old ICO with multi-size `favicon.ico`, PNG variants (`16x16`, `32x32`), `logo192.png` / `logo512.png`, and `apple-touch-icon.png` generated from the new brand mark
- Point `index.html` and `manifest.json` at the new assets; drop the CRA placeholder app name in the manifest

## Test plan
- [ ] Hard-refresh the app (or clear site data) and confirm the new logo appears in the browser tab
- [ ] Check DevTools Network for `favicon.ico` / PNG icons — no 404s and no requests for `favicon.jpg`
- [ ] On mobile Safari / iOS home-screen add, confirm apple-touch-icon looks correct
- [ ] Confirm PWA/manifest icons resolve to the new 192/512 assetsReviewed-on: #19

llm-fe/public/manifest.json

@@ -1,11 +1,21 @@
 {
   "short_name": "Chat by AI ML Operations. LLC",
-  "name": "Create React App Sample",
+  "name": "Chat by AI ML Operations, LLC",
   "icons": [
     {
       "src": "favicon.ico",
-      "sizes": "64x64 32x32 24x24 16x16",
+      "sizes": "64x64 48x48 32x32 24x24 16x16",
       "type": "image/x-icon"
+    },
+    {
+      "src": "logo192.png",
+      "type": "image/png",
+      "sizes": "192x192"
+    },
+    {
+      "src": "logo512.png",
+      "type": "image/png",
+      "sizes": "512x512"
     }
   ],
   "start_url": ".",