Update Gradle and Android SDK for modern compatibility

[muddxyii]

Objective

• Modernize build system to current Android development standards
• Fix Gradle 8.0 compatibility issues and deprecation warnings
• Update Java target to align with upstream PDFBox requirements

Solution

• Updated Android Gradle Plugin - Upgraded from 7.4.2 to 8.11.1 for latest tooling support
• Updated Android SDK versions - Upgraded compile/target SDK from 33 to 35 for current Android compatibility
• Upgraded Java compatibility - Updated from Java 1.7 to Java 1.8 to align with upstream PDFBox 3.x requirements
• Fixed Gradle deprecations - Updated task configuration syntax and property assignments

Testing

• Clean build successful - ./gradlew clean build completes without errors or warnings
• All unit tests pass - Existing test suite continues to pass with updated tooling
• Gradle compatibility confirmed - No more Gradle 8.0 deprecation warnings

Testing Steps:

1. Run ./gradlew clean build to verify successful build
2. Run ./gradlew test to confirm all tests pass
3. Verify no deprecation warnings during build process
4. Check that library functionality remains intact

Platforms tested:

• macOS with Android SDK 35 - builds successfully\