Add caps lock indicator and keyboard layout support

- Add caps lock ring color change when caps lock is enabled (matching swaylock-effects)
- Add configurable caps lock colors: ring, text, key highlight, backspace highlight
- Add show_caps_lock_text config option (enabled by default)
- Add keyboard layout display with show_keyboard_layout option (disabled by default)
- Change keyboard_layout from u32 to String for proper display
- Add rust-cache to CI and dbus-1-dev dependency

src/lock.rs

@@ -109,7 +109,6 @@ impl LockedSurface {
 
         // Update caps lock state in renderer
         self.renderer.caps_lock = self.input_handler.caps_lock();
-        log::debug!("Caps lock state: {}", self.input_handler.caps_lock());
 
         // Set background if available and not already applied
         if !self.background_applied {