Add Limine bootloader support with themed styling

Phase 2: Bootloader improvements

- Add bootloader choice: systemd-boot (default) or Limine
- Configure Limine with classical theme colors:
  - Dark brown background (#1a1611)
  - Tan text (#d4c4a8)
  - Gold accents (#d4a857)
- Add Plymouth boot splash option
- Update installer to prompt for bootloader choice
- Add example-limine configuration
- Update documentation with boot options

Users can now choose between:
1. systemd-boot - Simple, reliable, well-tested (default)
2. Limine - Modern, prettier, themed to match Nomarchy

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -27,6 +27,8 @@ Download the ISO from the releases page and boot from it for a fresh installatio
 - **SwayNC** - Notification center
 - **Neovim** - Fully configured with LSP support
 - **Classical Theme** - Earthy, vintage aesthetic inspired by historical paintings
+- **Bootloader Choice** - systemd-boot (default) or Limine (prettier, more features)
+- **Plymouth** - Optional boot splash screen
 
 ## Keybindings