refactor: update theme management and enhance UI components

- Refactored theme imports in `preferences.ts` and `ThemeSelector.tsx` to use centralized `theme-config`.
- Added new CSS variables for special cards in `globals.css` to improve theme consistency.
- Enhanced `Header` and `TaskCard` components with theme dropdown functionality for better user experience.
- Updated `ThemeProvider` to support cycling through dark themes, improving theme selection flexibility.
- Cleaned up unused imports and streamlined component structures for better maintainability.

src/app/layout.tsx

@@ -5,6 +5,7 @@ import { ThemeProvider } from "@/contexts/ThemeContext";
 import { JiraConfigProvider } from "@/contexts/JiraConfigContext";
 import { UserPreferencesProvider } from "@/contexts/UserPreferencesContext";
 import { userPreferencesService } from "@/services/core/user-preferences";
+import { KeyboardShortcuts } from "@/components/KeyboardShortcuts";
 
 const geistSans = Geist({
   variable: "--font-geist-sans",
@@ -38,6 +39,7 @@ export default async function RootLayout({
           initialTheme={initialPreferences.viewPreferences.theme}
           userPreferredTheme={initialPreferences.viewPreferences.theme === 'light' ? 'dark' : initialPreferences.viewPreferences.theme}
         >
+          <KeyboardShortcuts />
           <JiraConfigProvider config={initialPreferences.jiraConfig}>
             <UserPreferencesProvider initialPreferences={initialPreferences}>
               {children}