feat(update): launch-time update checker with snooze and dependency alerts

[mcoliver]

Summary

Addresses Issue #34.

This PR introduces automatic launch-time checking for OpenUTV updates, addressing user needs for polite notification, snooze controls, and Windows dependency update alerts without interrupting critical pipeline workflows.

Architectural Decisions

• Check & Alert (Non-blocking): We notify the user rather than forcing silent background updates in-place. Silently rewriting binaries during playback or session work can cause file locking, library collisions, or breaking active studio sessions.
• Snooze & Skip Controls:
  • Remind Me Tomorrow (1 Day): Mutes startup checks for 24 hours.
  • Remind Me in 1 Week (7 Days): Mutes startup checks for 7 days.
  • Skip This Version: Permanently suppresses alerts for the specific release version while still allowing future releases to be reported.
• Detached Startup Check: Initiated via detached background thread/process so UTV startup time is unaffected (0ms blocking latency).
• Windows OpenUTVDeps Detection: Inspects installed OpenUTVDeps runtime installations (directory patterns and Windows Uninstall registry) and queries GitHub releases for utv-dependencies, alerting users if their core runtime is outdated and providing a direct link or installer.
• Package Manager Integration:
  • macOS: Offers Homebrew Cask upgrade if installed via utv cask.
  • Windows: Offers Chocolatey / Scoop one-click command triggers if detected.

Changes

• Updated src/bin/nsapps/UTV/openutv-check-updates.py:
  • Added configuration persistence in update_settings.json (~/.openutv, %APPDATA%, or ~/Library/Application Support/OpenUTV).
  • Added --startup mode with a 3-second render settle delay and silent fallback.
  • Added multi-choice dialogs for macOS (AppleScript), Windows (Tkinter with MessageBoxW fallback), and Linux (Zenity / Kdialog).
  • Added Windows OpenUTVDeps version detection and utv-dependencies release querying.
• Updated src/plugins/rv-packages/visto_help_menu/openrv_help_menu_mode.mu:
  • Added checkUpdatesOnStartup() called asynchronously upon mode initialization.

Closes #34