Add XAUTHORITY, XDG_SESSION_DESKTOP, XDG_CURRENT_DESKTOP,
XDG_DATA_DIRS, and XDG_CONFIG_DIRS to session environment.
Expand PATH to include ~/.local/bin and ~/.cargo/bin.

Remove Wayland session enumeration since gardm runs an X
server and Wayland compositors cannot run on X11.

Switch from pam-client to pam crate for simpler API. Use
PasswordConv for non-interactive authentication and add
debug logging throughout the auth flow.

Simplify PAM config to use pam_unix.so directly instead of
Fedora-specific includes and SELinux modules.

Add systemd-logind integration for power actions (shutdown, reboot,
suspend) via D-Bus. Update system configuration for Fedora compatibility.

Changes:
- Add zbus dependency for D-Bus communication
- Add power.rs module with logind integration
- Update PAM config based on SDDM's Fedora configuration
- Update systemd service for better compatibility
- Add deployment scripts:
  - install.sh: installs binaries, configs, and service
  - test-gardm.sh: safe testing on separate VT/display
  - swap-dm.sh: safely swap from SDDM to gardm with rollback

Add theming system with customizable colors, fonts, and accessibility
options for the greeter UI.

Features:
- theme.rs with Color parsing (hex #RRGGBB, rgba(), rgb())
- Customizable colors: panel, text, accent, input, button
- Font family and size configuration
- High contrast mode with enhanced visibility
- Large text accessibility option (25% larger)
- Reduce motion option (disables fade transitions)
- All widgets updated to use theme values

Add monitor detection module using RandR to detect connected monitors,
their positions, and primary display. UI elements now center on the
primary monitor instead of the full virtual screen.

Changes:
- Add monitors.rs with MonitorConfig and Monitor structs
- Add randr feature to x11rb dependency
- Update LoginForm, UserList, PowerButtons to accept center coordinates
- Add root() accessor to GreeterWindow for RandR queries
- Add sprint documentation for sprints 5-8

- Avatar loading from ~/.face, AccountsService, and other standard paths
- Circular avatar rendering with RGBA to BGRA conversion
- Fallback to colored initials when no avatar found
- Horizontal user list above login form with hover effects
- Click user to populate username and focus password field
- Selection highlight with blue ring

- Custom Cairo-drawn icons (power, reboot, suspend, chevron, checkmark)
- Power buttons with color-coded hover highlights
- Session selector dropdown with list from daemon
- Mouse tracking for hover states
- IPC integration for power actions

- Read garbg config and playlist state for wallpaper resolution
- Greeter config with visual settings (blur, brightness, corner radius)
- Fade-out transition on successful login
- Relaxed socket permissions for development (0666)

- X11 window with fullscreen override redirect
- Cairo rendering surface for drawing
- Background loader with blur and brightness adjustment
- Login form widget with username/password fields
- Keyboard input handling with X11 keycodes
- IPC integration with gardmd for authentication