Migrate Termux to AGP 8, Gradle 8, and Android SDK 36

[Rimusolamus]

🧩 Summary

Modernize the Termux build setup for AGP 8 / Gradle 8 / SDK 36 and update dependencies.
Includes namespace migration, publishing improvements, and minor cleanups.

🔧 Changes

Bump Gradle → 8.13, AGP → 8.1.3, NDK → 26.3.11579264

Update compileSdk → 36, minSdk → 23

Add namespace to all modules

Replace lintOptions with new lint block

Enable buildFeatures.buildConfig in app module

Update AndroidX, Material, Guava, and testing dependencies

Use WindowMetricsCalculator in ViewUtils (API 30+ compliant)

Fix deprecated AlertDialog style reference

Replace @nullable import with AndroidX annotation

Remove obsolete manifest attributes and add stubs for AGP 8

Simplify Maven publishing (singleVariant("release") { withSourcesJar() })

Add new resources: bell.ogg, action_yes, action_no

✅ Motivation

Brings Termux up to date with the latest Android tooling, ensuring:

Compatibility with Android 14+ (API 34–36)

Cleaner and more maintainable Gradle configuration

Reliable library publishing and desugaring setup

Removal of deprecated APIs

🧪 Testing

Built and ran successfully on Android 14 (API 34) emulator

All modules compile under AGP 8.1.3 / Gradle 8.13 / JDK 11

With new ndk I was able to run project on arm macbook

🧭 Notes

Requires Gradle wrapper update (./gradlew wrapper --gradle-version 8.13)

Old Gradle 7.x projects or scripts may need minor adjustments

PS: It's my first open source PR ever so if I do something wrong, please let me know.