feat(android): scaffold Capacitor 8 native project + hardware Back button

Add @capacitor/{core,android,app,cli,assets} to ui/, a capacitor.config.ts (appId ru.eruditgame.app, appName Эрудит, webDir dist — bundle model, no server.url), and the generated ui/android/ Gradle project (tracked; build outputs and the machine-specific local.properties gitignored, keystore patterns un-commented so signing material can never be committed). Wire the Android hardware Back button in ui/src/lib/native.ts behind a dynamic @capacitor/app import (web/mock bundles never load it), called from App.svelte onMount and reusing routeDepth for the navigation-root check. Whitelist sharp in pnpm-workspace.yaml for @capacitor/assets icon generation.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ui/package.json

@@ -9,6 +9,8 @@
     "start": "vite --mode mock",
     "build": "vite build",
     "preview": "vite preview",
+    "cap:sync": "cap sync android",
+    "android:assets": "capacitor-assets generate --android",
     "check": "svelte-check --tsconfig ./tsconfig.json",
     "codegen": "rm -rf src/gen && flatc --ts -o src/gen/fbs ../pkg/fbs/scrabble.fbs && buf generate ../gateway --template buf.gen.yaml",
     "test:unit": "vitest run",
@@ -17,6 +19,9 @@
   },
   "dependencies": {
     "@bufbuild/protobuf": "^2.12.0",
+    "@capacitor/android": "^8.4.1",
+    "@capacitor/app": "^8.1.0",
+    "@capacitor/core": "^8.4.1",
     "@connectrpc/connect": "^2.1.0",
     "@connectrpc/connect-web": "^2.1.0",
     "@vkontakte/vk-bridge": "^3.0.2",
@@ -24,6 +29,8 @@
   },
   "devDependencies": {
     "@bufbuild/protoc-gen-es": "^2.12.0",
+    "@capacitor/assets": "^3.0.5",
+    "@capacitor/cli": "^8.4.1",
     "@playwright/test": "^1.49.0",
     "@sveltejs/vite-plugin-svelte": "^5.0.0",
     "@types/node": "^22.10.0",