New OverlayController (core/overlay_controller.py):
- DESKTOP_APP: Activity bar only in desktop app
- OVERLAY_ALWAYS: Always visible as overlay
- OVERLAY_GAME_FOCUSED: Only when EU game window focused
- OVERLAY_HOTKEY_TOGGLE: Toggle with Ctrl+Shift+B (default)
- OVERLAY_TEMPORARY: Show 8 seconds on hotkey, then auto-hide
Changes:
- Activity bar now controlled by OverlayController
- Removed old _start_eu_focus_detection/_check_eu_focus methods
- Updated quit() to stop overlay controller
- Startup messages show current mode
Settings key: activity_bar.overlay_mode
Default: overlay_toggle