Create GitHub Actions build workflow with auto-updater JSON generation

[Copilot]

This PR implements a comprehensive GitHub Actions build workflow using tauri-apps/tauri-action that automatically builds the Tauri application for multiple platforms and generates an updater JSON file for seamless auto-updates.

Key Features

Multi-Platform Build Support

The workflow builds the application for all major platforms:

• macOS (Apple Silicon - aarch64)
• macOS (Intel - x86_64)
• Linux (x86_64)
• Windows (x86_64)

Auto-Updater Integration

• Configures Tauri's updater plugin in tauri.conf.json with GitHub releases as the update endpoint
• Adds tauri-plugin-updater dependency and initializes it in the Rust code
• Automatically generates updater.json file following Tauri v2 specification format
• Includes cryptographic signature verification for secure updates

Release Automation

The release workflow:

1. Creates draft releases for review
2. Builds and uploads platform-specific artifacts
3. Generates and uploads the updater JSON with proper platform detection
4. Publishes the release automatically

CI/CD Pipeline

Includes a CI workflow that tests builds on pull requests and pushes to ensure code quality and compilation integrity.

Usage

To create a new release:

git tag v1.0.3
git push origin v1.0.3

The workflow handles everything automatically, enabling users to receive seamless updates through the Tauri updater system.

Additional Improvements

• Fixed HTML syntax error in src/app.html
• Added missing @eslint/js dependency
• Created comprehensive documentation in BUILD.md
• Validated all YAML configurations

This implementation provides the foundation for issue #23 (auto-updater functionality) by setting up the complete build and release infrastructure needed for automatic application updates.

Fixes #25.

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