feat(ui): Symbole fuer Tab, Startbildschirm und Manifest (#017)

npm run icons erzeugt SVG, ICO und PNG aus den Vorlagen in assets/. Fuer kleine
Groessen kommen die vereinfachten Fassungen zum Einsatz.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "proxledger",
-  "version": "0.12.0",
+  "version": "0.12.1",
   "private": true,
   "scripts": {
     "dev": "next dev",
@@ -24,7 +24,8 @@
     "build:worker": "esbuild src/worker/index.ts --bundle --platform=node --target=node24 --format=esm --outfile=dist/worker.mjs --banner:js=\"$(cat deploy/worker-banner.js)\" --external:@prisma/client --external:@node-rs/argon2 --external:pg-native",
     "build:all": "npm run build && npm run build:worker",
     "lasttest": "tsx scripts/lasttest.ts",
-    "screenshots": "node scripts/screenshots.mjs"
+    "screenshots": "node scripts/screenshots.mjs",
+    "icons": "node scripts/icons.mjs"
   },
   "dependencies": {
     "@node-rs/argon2": "^2.2.1",
@@ -55,6 +56,7 @@
     "eslint-config-prettier": "^10.1.8",
     "prettier": "^3.9.7",
     "prisma": "^7.10.0",
+    "sharp": "^0.35.4",
     "tsx": "^4.23.13",
     "typescript": "^5",
     "vitest": "^5.0.1"