Harden Docker packaging and bundle frontend assets locally

- replace fragile Docker file bind mount with persistent /data storage
- add container entrypoint to link config.json from persistent storage
- tighten Docker image permissions and add a basic healthcheck
- add .dockerignore to keep git metadata and runtime files out of the image
- bundle hls.js locally instead of loading it from a CDN
- download and serve UI/theme fonts locally instead of Google Fonts
- update service worker cache entries for local assets
- refresh README to reflect local bundled assets and cleaner deployment docs

sw.js

@@ -1,14 +1,14 @@
-const CACHE_NAME = 'gridtv-v1';
+const CACHE_NAME = 'gridtv-v2';
 
 // Ressources statiques à mettre en cache immédiatement
 const STATIC_ASSETS = [
   '/',
   '/index.php',
   '/manifest.json',
+  '/assets/fonts/fonts.css',
   '/assets/icon-192.png',
   '/assets/icon-512.png',
-  'https://fonts.googleapis.com/css2?family=Share+Tech+Mono&family=Barlow+Condensed:wght@300;400;600;700&display=swap',
-  'https://cdnjs.cloudflare.com/ajax/libs/hls.js/1.4.12/hls.min.js'
+  '/assets/vendor/hls.min.js'
 ];
 
 // Install : mise en cache des assets statiques