Implement BenthicBloom GNOME 50 wallpaper extension

Adds a complete GNOME Shell 50 extension with folder-based wallpaper
auto-rotation (shuffle/sequential, crossfade transitions, lock screen
sync), GStreamer-backed live/video wallpapers rendered onto the shell's
own Clutter stage, and OLED burn-in protection (pixel shifting, idle
dimming, forced periodic rotation). Includes a top-bar quick-access
indicator, a libadwaita preferences window, GSettings schema, and a
Makefile for install/packaging.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019RDqbdjsiisSU7CbQke4g8

lib/settingsKeys.js

@@ -0,0 +1,34 @@
+export const SettingsKey = Object.freeze({
+    SHOW_INDICATOR: 'show-indicator',
+    DEBUG_LOGGING: 'debug-logging',
+    WALLPAPER_FOLDERS: 'wallpaper-folders',
+    APPLY_TO_LOCK_SCREEN: 'apply-to-lock-screen',
+
+    ROTATION_ENABLED: 'rotation-enabled',
+    ROTATION_INTERVAL_SECONDS: 'rotation-interval-seconds',
+    ROTATION_MODE: 'rotation-mode',
+    CURRENT_INDEX: 'current-index',
+    TRANSITION_ENABLED: 'transition-enabled',
+    TRANSITION_DURATION_MS: 'transition-duration-ms',
+
+    LIVE_WALLPAPER_ENABLED: 'live-wallpaper-enabled',
+    LIVE_WALLPAPER_PATH: 'live-wallpaper-path',
+    LIVE_WALLPAPER_MUTED: 'live-wallpaper-muted',
+    LIVE_WALLPAPER_PLAYBACK_RATE: 'live-wallpaper-playback-rate',
+    LIVE_WALLPAPER_PAUSE_ON_BATTERY: 'live-wallpaper-pause-on-battery',
+    LIVE_WALLPAPER_PAUSE_WHEN_FULLSCREEN: 'live-wallpaper-pause-when-fullscreen',
+
+    OLED_PROTECTION_ENABLED: 'oled-protection-enabled',
+    OLED_PIXEL_SHIFT_ENABLED: 'oled-pixel-shift-enabled',
+    OLED_PIXEL_SHIFT_INTERVAL_SECONDS: 'oled-pixel-shift-interval-seconds',
+    OLED_PIXEL_SHIFT_AMOUNT_PX: 'oled-pixel-shift-amount-px',
+    OLED_DIM_ON_IDLE_ENABLED: 'oled-dim-on-idle-enabled',
+    OLED_DIM_IDLE_DELAY_SECONDS: 'oled-dim-idle-delay-seconds',
+    OLED_DIM_BRIGHTNESS: 'oled-dim-brightness',
+    OLED_FORCE_ROTATION_ENABLED: 'oled-force-rotation-enabled',
+    OLED_MAX_STATIC_DURATION_SECONDS: 'oled-max-static-duration-seconds',
+});
+
+export const IMAGE_EXTENSIONS = Object.freeze([
+    '.jpg', '.jpeg', '.png', '.webp', '.bmp', '.tiff', '.tif', '.gif',
+]);