Add system tray menu and controls

[grovecj]

Description

Implement system tray icon with context menu for quick access.

Tasks

• Create app icon for tray (Windows .ico, macOS template image)
• Build context menu with options:
  • Start Capture
  • Open Recent GIF
  • Settings
  • About
  • Quit
• Show recording status in tray (icon change)
• Double-click to start capture (optional)
• Minimize to tray instead of taskbar (optional)

Menu Structure

[Icon]
├── Start Capture (Ctrl+Shift+G)
├── Recent GIFs ►
│   ├── clip_2025-01-01.gif
│   └── clip_2024-12-31.gif
├── ─────────────
├── Settings...
├── About Gif Clipper
├── ─────────────
└── Quit

Acceptance Criteria

• Tray icon visible on both Windows and macOS
• Context menu provides quick access to all features
• Icon changes during recording