feat: enhance login page with random theme and background features

- Added RandomThemeApplier to apply a random theme on login.
- Introduced RandomBackground component for setting a random background from presets.
- Updated GlobalKeyboardShortcuts import in RootLayout for consistent keyboard shortcut handling.
- Refactored BackgroundContext to include cycleBackground functionality for dynamic background changes.
- Removed deprecated useBackgroundCycle hook to streamline background management.

src/components/GlobalKeyboardShortcuts.tsx

@@ -1,10 +1,10 @@
 'use client';
 
 import { useGlobalKeyboardShortcuts } from '@/hooks/useGlobalKeyboardShortcuts';
-import { useBackgroundCycle } from '@/hooks/useBackgroundCycle';
+import { useBackground } from '@/contexts/BackgroundContext';
 
 export function GlobalKeyboardShortcuts() {
-  const { cycleBackground } = useBackgroundCycle();
+  const { cycleBackground } = useBackground();
 
   useGlobalKeyboardShortcuts({
     onCycleBackground: cycleBackground