- Use /usr/local/bin/garbg path
- Target graphical-session.target
- Clean up service definition

Session startup:
- Add sd-notify for READY=1 signaling when socket is listening
- Remove retry hacks (connect_with_retry, send_command_with_retry)
- Remove X11 health check timer (PartOf=gar-session.target handles lifecycle)
- Daemon now fails fast if X11 unavailable - systemd handles ordering

Multi-monitor support (Phase 5.3):
- Add RandR-based monitor detection via Monitor::get_all()
- Add Compositor for multi-monitor wallpaper compositing
- Support set-monitor command for per-monitor wallpapers
- Handle monitor hotplug events from gar

Enhanced IPC:
- Add QueryMonitors, QueryCurrent, SetMonitor commands
- Add monitor event subscription to gar client

This enables race-condition-free startup when used with
gar-session.target and Type=notify systemd service.

- GIF decoder with frame-by-frame access and timing
- Double-buffered X11 rendering for smooth animation
- Animation event loop integrated into daemon
- CLI --animate flag and --max-fps option
- X11 error handling improvements

- X11 wallpaper setting with image scaling
- Local, HTTP, and GitHub source providers
- Playlist state with shuffle/wrap-around
- Daemon mode with IPC and slideshow timer
- Optional gar workspace integration
- Systemd user service file