feat(pwa): loading screen in the colours of the last used theme

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/public/sw.js

@@ -7,7 +7,7 @@
 //   would hand it the old values), the cache only offline.
 // - API requests are never touched; offline data comes from the app's own cache (lib/offline.ts).
 // Raise VERSION when this file changes in a way that needs fresh caches.
-const VERSION = 'v5';
+const VERSION = 'v6';
 const SHELL_CACHE = `mindsift-shell-${VERSION}`;
 const ASSET_CACHE = `mindsift-assets-${VERSION}`;
 const MAX_ASSETS = 80;
@@ -23,6 +23,8 @@ const SHELL_URLS = [
   '/icon-512x512.png',
   '/apple-touch-icon.png',
   '/badge-96x96.png',
+  '/boot-theme.js',
+  '/pwa-install.js',
 ];
 
 self.addEventListener('install', (event) => {