fix(frontend): contain hover-video to miximage frame + restore dev HMR

The miximage hover video had no height bound, so a tall/narrow source
overflowed the cover. Match the miximage frame's box and `object-fit:
cover` it so the clip fills the bezel screen and crops instead of
spilling past it.

Also gate the PWA dev service worker behind DEV_PWA: it intercepted dev
requests and forced full page reloads on every edit (CSS included),
defeating HMR. Default dev now gets working HMR; set DEV_PWA=true to test
the PWA in dev.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/v2/components/shared/GameCover.vue

@@ -358,9 +358,10 @@ defineExpose({
 .game-cover__video {
   position: absolute;
   top: 0.75rem;
-  left: 0.35rem;
+  left: 0.3rem;
   width: 97%;
-  object-fit: contain;
+  aspect-ratio: 745 / 550;
+  object-fit: cover;
   opacity: 0;
   transition: opacity 0.35s ease;
   pointer-events: none;

frontend/vite.config.js

@@ -67,6 +67,10 @@ export default defineConfig(({ mode }) => {
   const backendPort = env.DEV_PORT ?? "5000";
   // const devMode = env.DEV_MODE === "true";
   const httpsMode = env.DEV_HTTPS === "true";
+  // The PWA service worker intercepts dev requests and forces full page
+  // reloads on edits (CSS included), defeating HMR. Keep it off in dev unless
+  // explicitly testing the PWA (DEV_PWA=true).
+  const pwaDevEnabled = env.DEV_PWA === "true";
 
   return {
     optimizeDeps: {
@@ -96,7 +100,7 @@ export default defineConfig(({ mode }) => {
           ],
         },
         devOptions: {
-          enabled: true,
+          enabled: pwaDevEnabled,
           type: "module",
         },
       }),