Set up Capacitor for Android and iOS builds

[JesseRWeigel]

Set up Capacitor to wrap the web app as native Android/iOS apps.

Steps:

• Install @capacitor/core and @capacitor/cli
• Init with app ID com.jesseweigel.battlemath
• Add android and ios platforms
• Configure capacitor.config.ts
• Sync build output
• Test in Android Studio emulator

This enables app store distribution.

Acceptance criteria:

• Capacitor configured
• Android project generated
• Build syncs correctly
• App runs in Android emulator