build: Android APK builds working — debug (8.9MB) and release (2.0MB)

- Fix C++ std::std:: double namespace in oboe_bridge.cpp
- Auto-fetch Oboe headers from GitHub in build.rs
- Configure cargo cross-compilation (.cargo/config.toml) with NDK linkers
- Fix Gradle settings (dependencyResolutionManagement), signing configs,
  Compose LinearProgressIndicator API, and Android manifest theme
- Add Gradle wrapper, .gitignore for build artifacts
- arm64-v8a only (raptorq crate incompatible with armv7 32-bit)
- Release APK: 2.0MB signed with wzp-release key
- Debug APK: 8.9MB signed with wzp-debug key

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

android/gradlew

@@ -0,0 +1,5 @@
+#!/bin/sh
+# Gradle wrapper script
+APP_HOME=$(cd "$(dirname "$0")" && pwd)
+CLASSPATH="$APP_HOME/gradle/wrapper/gradle-wrapper.jar"
+exec java -classpath "$CLASSPATH" org.gradle.wrapper.GradleWrapperMain "$@"