Add Capacitor Android packaging (APK) for Cafe Bazaar / Myket

- Next static export (output: export) wrapped by Capacitor; appId
  com.bargevasat.app, appName «برگ وسط»
- android/ native project + @capacitor/app; hardware back handled by
  CapacitorBack (back a screen, exit at home)
- npm scripts (cap:sync, android:open, android:apk), ANDROID.md
- Gradle Maven-mirror init-script template (dl.google.com/Maven Central are
  blocked in Iran — same reason NuGet is mirrored)

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

.gitignore

@@ -17,6 +17,11 @@
 /.next/
 /out/
 
+# capacitor copied web assets + machine-specific android files
+/android/app/src/main/assets/public
+/android/local.properties
+/android/gradle-mirror.init.gradle
+
 # production
 /build