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

package.json

@@ -12,7 +12,8 @@
 		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",
 		"test:e2e": "playwright test",
 		"lint": "prettier --check .",
-		"format": "prettier --write ."
+		"format": "prettier --write .",
+		"test:pwa": "playwright test -c playwright.pwa.config.ts"
 	},
 	"devDependencies": {
 		"@fontsource-variable/geist": "^5.2.9",
@@ -25,6 +26,7 @@
 		"@tailwindcss/typography": "^0.5.19",
 		"@tailwindcss/vite": "^4.3.0",
 		"@types/node": "^26.3.0",
+		"@vite-pwa/sveltekit": "^1.1.0",
 		"bits-ui": "2.18.1",
 		"class-variance-authority": "0.7.1",
 		"clsx": "2.1.1",
@@ -39,7 +41,9 @@
 		"tailwindcss": "^4.3.0",
 		"tw-animate-css": "^1.4.0",
 		"typescript": "^6.0.3",
-		"vite": "^8.0.16"
+		"vite": "^8.0.16",
+		"vite-plugin-pwa": "^1.3.0",
+		"workbox-window": "^7.4.1"
 	},
 	"dependencies": {
 		"@cantoo/pdf-lib": "^2.9.1",