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/android/app/capacitor.build.gradle

@@ -0,0 +1,19 @@
+// DO NOT EDIT THIS FILE! IT IS GENERATED EACH TIME "capacitor update" IS RUN
+
+android {
+  compileOptions {
+      sourceCompatibility JavaVersion.VERSION_21
+      targetCompatibility JavaVersion.VERSION_21
+  }
+}
+
+apply from: "../capacitor-cordova-android-plugins/cordova.variables.gradle"
+dependencies {
+    implementation project(':capacitor-app')
+
+}
+
+
+if (hasProperty('postBuildExtras')) {
+  postBuildExtras()
+}