feat(android): generate launcher icons from zeavis-logo.svg during CI build

- Add scripts/generate-icons.js using sharp to convert SVG to PNG
  at all Android density buckets (mdpi 48→xxxhdpi 192)
- Add sharp as devDependency
- Update CI workflow to run icon generation after tauri android init
- Replaces Tauri's default icons with ZeaVis Edu logo

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

apps/tauri/package.json

@@ -12,5 +12,8 @@
   },
   "devDependencies": {
     "@tauri-apps/cli": "^2"
+  },
+  "dependencies": {
+    "sharp": "0.35.1"
   }
 }