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/app/layout.tsx

@@ -58,8 +58,8 @@ export default async function RootLayout({
                 <KeyboardShortcuts />
                 <JiraConfigProvider config={initialPreferences?.jiraConfig || { enabled: false }}>
                   <UserPreferencesProvider initialPreferences={initialPreferences}>
-                    <GlobalKeyboardShortcuts />
                     <BackgroundProvider>
+                      <GlobalKeyboardShortcuts />
                       {children}
                     </BackgroundProvider>
                   </UserPreferencesProvider>