Add native settings bridge, CLI auto-detection, error handlers and CLI-aware buttons; improve macOS menu & layout fixes

• Add native settings integration:

  • Introduce SettingsService / Settings bridge on macOS for get/set settings and showSettings.
  • Add macOS native window code (SettingsWindow.swift/MainFlutterWindow changes) and AppDelegate wiring to insert a Settings menu item and a settings method channel.
  • Provide methods to show a native Settings window and handle setting change notifications; add logging for settings flows.

• CLI improvements:

  • Convert initCli to async and call it at startup.
  • Make Cli.init asynchronous and add auto-detection of common CLI tools (ffmpeg, ffprobe, gallery-dl, gifski, yt-dlp) on macOS; store detected paths via settings.
  • Add helper functions isFFmpegAvailable/isFFprobeAvailable and safer process handling (noThrow) across video utilities and ffprobe/ffmpeg calls.
  • Update video utils and process calls to check exit codes and log failures.

• UI / UX and layout fixes:

  • Replace nested unbounded SingleChildScrollView in main UI with bounded SizedBox/MouseRegion to avoid layout constraints.
  • Add a small settings button in the drop section to open native settings.
  • Improve setup UI: provide "Install FFmpeg Manually" button when FFmpeg install step failed, and add a helper to launch FFmpeg guide.
  • Update macOS status item behavior: respect "showMenuBarIcon" setting, create/hide menu item accordingly; set tray icon with fallbacks and add extensive logging.
  • Raise macOS deployment target to 11.0 in Xcode project.

• Error handling and retry:

  • Centralize error UI using new ErrorHandler widget in archive/minify/misc sections.
  • Add retryTrigger ValueNotifier and listeners for minify/archive/misc settings to allow retrying failed operations.
  • Ensure progress notifiers disposal where appropriate.

• CLI-aware UI components:

  • Introduce/Use CliAwareButton for buttons that depend on external CLI tools; provide required tools lists for Archive/Minify/Misc operations and disable UI if tools missing.

• Misc:

  • Update various package versions in oss_licenses.dart.
  • Minor state and formatting fixes.
  • Add new files to project (error handler widget, services, settings bridge files, tray assets) — see diff for full list.

Full Changelog: https://github.com/foamify/shakepin/compare/v0.3.6...v0.4.0