pwa / offline mode

- @vite-pwa/sveltekit: workbox precache (incl. pdfjs worker), generated manifest, prompt-style updates via PwaUpdatePrompt toast
- prerendered routes for offline navigation, PWA icons, theme-color + apple-touch-icon
- pwa offline/update e2e suite (pnpm test:pwa, playwright.pwa.config.ts)
- datenschutz: offline/install section; prettier cleanup of shadcn components

agents.md

@@ -22,6 +22,7 @@ The application also contains German imprint and privacy-policy routes.
 - fflate for ZIP extraction and image-export ZIP creation
 - pdf-lib for PDF assembly, `@cantoo/pdf-lib` for encryption, and pdfjs-dist for rendering
 - `@sveltejs/adapter-node`
+- PWA/offline support through `@vite-pwa/sveltekit` (Workbox precache, generated web manifest)
 - pnpm with a committed lockfile
 - Prettier with Svelte and Tailwind plugins
 
@@ -37,6 +38,7 @@ pnpm preview             # Preview the production build
 pnpm check               # Run Svelte and TypeScript diagnostics
 pnpm check:watch         # Run diagnostics in watch mode
 pnpm test:e2e            # Run the Playwright toolbox tests in Chromium
+pnpm test:pwa            # PWA offline/update tests against the production build (requires pnpm build)
 pnpm lint                # Check repository formatting with Prettier
 pnpm format              # Format the repository with Prettier
 ```
@@ -75,6 +77,7 @@ src/
 │   │   ├── FileDropzone.svelte           # Shared PDF/image/ZIP file picker and drop target
 │   │   ├── ZipFilePicker.svelte          # Compact ZIP picker button with hidden resettable input
 │   │   ├── PdfPageGrid.svelte            # Accessible PDF thumbnail selection grid
+│   │   ├── PwaUpdatePrompt.svelte        # Service-worker registration and update/offline toast
 │   │   ├── RasterizationWarning.svelte
 │   │   ├── ZipDropzone.svelte            # beA-specific wrapper around FileDropzone
 │   │   ├── icons/                        # Project-specific SVG components
@@ -92,6 +95,7 @@ src/
 │   └── zip-processing.ts                 # Archive model, transforms, and PDF export
 └── routes/
     ├── +layout.svelte                    # Shared logo header and branded footer
+    ├── +layout.ts                        # `prerender = true` for all routes (PWA offline documents)
     ├── +page.svelte                      # Toolbox hub and global beA ZIP drop target
     ├── layout.css                        # Tailwind, shadcn, theme, fonts, global CSS
     ├── tools/
@@ -100,15 +104,42 @@ src/
     │   └── {merge,separate,stamp,watermark,encrypt,decrypt,compress,convert,rotate,metadata}/
     ├── datenschutz/+page.svelte          # Privacy policy
     └── impressum/+page.svelte            # Imprint
-static/                                   # Public logo, footer art, and robots.txt
+static/                                   # Public logo, footer art, PWA icons, and robots.txt
 components.json                           # shadcn-svelte registry configuration
 Dockerfile                                # Node adapter production image
+playwright.pwa.config.ts                  # Playwright config for `pnpm test:pwa`
 plan/                                     # Design and implementation notes
 ```
 
 Generated directories such as `.svelte-kit/`, `build/`, and `node_modules/` must not be edited or
 committed.
 
+## PWA / offline mode
+
+- `SvelteKitPWA` is configured in `vite.config.ts` with `registerType: 'prompt'`: a waiting service
+  worker never activates by itself. `PwaUpdatePrompt.svelte` registers the worker in the browser and
+  shows a toast (“Neue Version verfügbar” with “Neu laden”/“Später”, plus a one-time hint when the
+  app is ready offline). Never force a reload — an in-progress archive must survive a declined
+  update.
+- All routes are prerendered (`src/routes/+layout.ts`), so route documents land in the precache and
+  offline navigation works for every page, including a direct deep link. `navigateFallback: '/'`
+  covers unknown paths.
+- Precache contents come from `workbox.globPatterns`: the plugin's client/prerendered defaults plus
+  `mjs` (the pdfjs worker chunk, required for offline rendering) and the local fonts; the unused
+  `static/Nunito/**` font drop is excluded via `globIgnores`. Precache size is ~4.5 MB.
+- PWA icons in `static/icons/` (192/512, maskable, apple-touch) were generated once from
+  `static/favicon.svg`; regenerate them with ImageMagick/rsvg if the logo changes. The manifest link
+  is injected client-side from `virtual:pwa-info` in the root layout, `theme-color` and the
+  apple-touch-icon live in `app.html`.
+- `devOptions.enabled` stays `false`: `pnpm dev` never registers a service worker, so development
+  caches stay clean. Verify PWA behaviour only against a production build (`pnpm build` and
+  `pnpm preview`, or `pnpm test:pwa`, which also covers the offline processing chain and the update
+  toast).
+- Simulating a deployment in tests requires restarting `node build/index.js`: adapter-node's static
+  handler (sirv, non-dev mode) walks the build directory once at startup and caches the ETags, so
+  swapped files are invisible to a running process. Browsers revalidate `/sw.js` via its ETag on
+  navigation and `registration.update()`, so the normal container restart on deploy is sufficient.
+
 ## Application flow and state
 
 - `/` is the toolbox hub. A ZIP dropped anywhere on that route is queued in memory and forwarded to