feat: enable r8 minify on release

[ovitrif]

Closes #1183

This PR enables R8 shrinking on release builds.

Description

• Turns on the AGP 9.3 optimization block for release, which includes the default Android keep rules.
• Keeps JNI types from the local Bluetooth AAR and its helper JAR.
• Sets the Kotlin compiler flag -Xannotation-default-target=param-property.
• Consumes bitkit-core-android 0.5.9, ldk-node-android 0.7.0-rc.64, vss-client-android 0.5.24, and paykit-android 0.1.0-rc47.

Preview

N/A — build configuration.

QA Notes

Manual Tests

• 1. Install minified devRelease on medium_phone (ARM64, API 36) → launch: app opens.
• 2. Terms → Skip Intro → New Wallet: Home is shown.
• 3. New Wallet → node start: Lightning node is running.
• 4. Home after node start: on-chain wallet syncs over Electrum SSL.
• 5. Home after node start: trusted Lightning peer connects.
• 6. New Wallet → VSS setup: store id is derived.
• 7. New Wallet → VSS setup: putObject succeeds.
• 8. Launch → Paykit init: native library loads.
• 9. Launch → bitkit-core init: native library loads.
• 10. Launch → Bluetooth init: btleplug initializes.
• 11. Settings → Hardware Wallets → Add Hardware Wallet: intro sheet opens.
• 12. Hardware Wallet intro → Continue: BLE scan starts.
• 13. Home after launch: HTTPS currency rates refresh.
• 14. Home → Receive: LN receive completes.
• 15. Home → Send: LN send completes.
• 16. Home → Receive: on-chain receive completes.
• 17. Home → Send: on-chain send completes.
• 18. Contacts → Paykit payment: contact payment completes.
• 19. Settings → Backup → restore on a new install: VSS restore completes.
• 20. Settings → Hardware Wallets → connect a real device: wallet pairs.
• 21. Hardware Wallet → transfer: transfer completes.
• 22. 16kb-page emulator → install minified devRelease → launch: app opens.

Automated Checks

• Local verification: just compile, just test, and just lint.
• R8 configuration analyzer: :app:analyzeDevReleaseR8Config.