Migrate CI from AppVeyor to GitHub Actions with Python 3.14 support

[Copilot]

Replaces AppVeyor CI configuration with GitHub Actions workflow that builds Python 3.14 for Android, Darwin (iOS/macOS), Linux, and Windows.

Changes

Workflow (.github/workflows/build-python.yml)

• 4 platform-specific jobs matching original AppVeyor matrix
• Android: NDK r27, all ABIs (arm64-v8a, armeabi-v7a, x86_64, x86)
• Darwin: iOS + macOS via BeeWare Python-Apple-support
• Linux: x86_64_v2 + aarch64 via python-build-standalone
• Windows: amd64 from official installer
• Explicit permissions: contents: write on all jobs
• Artifact uploads + release deployment on version tags

Version Updates

• PYTHON_VERSION: 3.14.0 (from 3.12.9)
• PYTHON_VERSION_SHORT: 3.14 (from 3.12)
• Windows install path: C:\python314-dist

Repository

• .appveyor.yml → .appveyor.yml.archived (preserved for rollback)
• .gitignore excludes build artifacts
• Updated README with platform details
• Added MIGRATION_NOTES.md with version adjustment guide

Triggers

• Push/PR to python-3.* or main branches
• Manual dispatch
• Tag push (e.g., v3.14) for release creation

Note

Python 3.14.0 may not be available yet. If builds fail, adjust to 3.13.x per MIGRATION_NOTES.md.

Original prompt

by analyzing the branch python-3.12, modify its appveyor.yml to github actions, and support python 3.14 builds for android, darwin, linux and windows.

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