Add GitHub Actions workflows with manual triggers

[sujithatzackriya]

Pull Request: Add GitHub Actions CI/CD Workflows

Description

Add GitHub Actions CI/CD workflows with manual-only triggers for building, testing, and releasing Meetily. This includes 8 workflow files and 3 documentation files.

Workflows added:

• build.yml - Reusable build workflow (called by other workflows)
• build-test.yml - Multi-platform test builds with signing
• build-macos.yml - macOS standalone builds (Apple Silicon)
• build-windows.yml - Windows standalone builds (x64)
• build-linux.yml - Linux builds (Ubuntu 22.04/24.04) - for development/testing only
• build-devtest.yml - Fast development builds (signing optional)
• release.yml - Production release workflow (macOS + Windows only)
• pr-main-check.yml - Quick validation check

Documentation added:

• WORKFLOWS_OVERVIEW.md - Complete guide to all workflows
• README_DEVTEST.md - DevTest workflow usage guide
• ACCELERATION_GUIDE.md - GPU acceleration documentation

Note: Production releases (release.yml) only build for macOS and Windows. Linux builds are available via build-linux.yml for development/testing purposes.

Related Issue

N/A - Initial CI/CD setup

Type of Change

• Bug fix
• New feature
• Documentation update
• Performance improvement
• Code refactoring
• Other (please describe)

Testing

• Unit tests added/updated
• Manual testing performed
• All tests pass

Documentation

• Documentation updated
• No documentation needed

Checklist

• Code follows project style
• Self-reviewed the code
• Added comments for complex code
• Updated README if needed
• Branch is up to date with devtest
• No merge conflicts

Screenshots (if applicable)

N/A - No UI changes

Additional Notes

All workflows use manual triggers only (workflow_dispatch). There are no automatic triggers from push or pull request events.

Version auto-increment: If a release tag (e.g., v0.1.1) already exists, the release workflow automatically increments to a minor version (v0.1.1.1, v0.1.1.2, etc., up to v0.1.1.100).

First test: Run the Validation Check workflow from the Actions tab to verify configuration.