feat: complete Pi Mobile revival roadmap

[ayagmar]

Summary

• align the Android client and bridge with the Pi 0.80.6 RPC/session contract
• add cursor-based incremental session reconstruction, invalidation recovery, and authoritative active-session topology
• harden bridge authentication, process limits, imports, session locks, and network defaults
• decompose the chat feature and improve onboarding, navigation, recovery, and connection diagnostics
• modernize the Android/Compose toolchain, CI, token storage, release docs, and contributor guidance
• add terminal QR pairing with pnpm pair and keep Hosts accessible for connection recovery
• fix Jump to latest indexing and stabilize the chat composer/keyboard layout

Verification

• ./gradlew clean ktlintCheck detekt test :app:lintDebug :app:assembleDebug :app:assembleRelease :app:compileDebugAndroidTestKotlin
• (cd bridge && pnpm install --frozen-lockfile && pnpm run check && pnpm audit --prod)
• debug APK installed successfully over wireless ADB
• bridge: 60 tests passing and no known production vulnerabilities