perf: cache Kokoro TTS model in service worker

Add CacheFirst runtimeCaching rules for Hugging Face model requests
(huggingface.co and cdn-lfs) with 90-day expiration. Add
getKokoroProgress() export to tts.ts for tracking download progress.
Add TTS model download progress bar overlay in FightViewer.vue that
shows during model loading and auto-hides when complete.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/vite.config.ts

@@ -58,6 +58,16 @@ export default defineConfig({
             method: 'GET',
             options: { cacheName: 'api-cache' },
           },
+          {
+            urlPattern: /^https:\/\/huggingface\.co\/.*Kokoro.*\.onnx/i,
+            handler: 'CacheFirst',
+            options: { cacheName: 'kokoro-model', expiration: { maxEntries: 10, maxAgeSeconds: 60 * 60 * 24 * 90 } },
+          },
+          {
+            urlPattern: /^https:\/\/cdn-lfs.*\.huggingface\.co\/.*/i,
+            handler: 'CacheFirst',
+            options: { cacheName: 'kokoro-model-lfs', expiration: { maxEntries: 20, maxAgeSeconds: 60 * 60 * 24 * 90 } },
+          },
         ],
       },
     }),