feat(ui): add PWA support with vite-plugin-pwa

- Add vite.config.pwa.ts extending the base config with VitePWA plugin
- Generate PWA icons at build time from source logo via @vite-pwa/assets-generator
- Add web app manifest with name, theme color, display overrides
- Add Workbox runtime caching: NetworkFirst for API, CacheFirst for assets
- Set navigateFallback to null to preserve server-side auth redirects
- Server build uses build:pwa for PWA-enabled output; Electron/Tauri use
  the base build without PWA

Signed-off-by: Jesper Derehag <jderehag@hotmail.com>

packages/server/package.json

@@ -18,7 +18,7 @@
   },
   "scripts": {
     "build": "npm run build:ui && npm run prepare-ui && tsc -p tsconfig.json && node ./scripts/copy-auth-pages.mjs && npm run prepare-config",
-    "build:ui": "npm run build --prefix ../ui",
+    "build:ui": "npm run build:pwa --prefix ../ui",
     "prepare-ui": "node ./scripts/copy-ui-dist.mjs",
     "prepare-config": "node ./scripts/copy-opencode-config.mjs",
     "dev": "cross-env CODENOMAD_DEV=1 CODENOMAD_SERVER_PASSWORD=codenomad-dev CLI_UI_DEV_SERVER=http://localhost:3000 tsx src/index.ts",