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

metadata.json

@@ -0,0 +1,11 @@
+{
+    "uuid": "benthicbloom@quinta0.github.io",
+    "name": "BenthicBloom",
+    "description": "Automatically rotates your wallpaper from folders you choose, supports looping video live wallpapers, and includes built-in pixel-shifting and idle-dimming to protect OLED displays from burn-in.",
+    "shell-version": ["50"],
+    "url": "https://github.com/quinta0/benthicbloom",
+    "settings-schema": "org.gnome.shell.extensions.benthicbloom",
+    "gettext-domain": "benthicbloom",
+    "version": 1,
+    "version-name": "1.0.0"
+}