style(ui): improve mobile responsiveness of status and navigation components

Refactor component spacing, typography, and layout to better support mobile
devices while maintaining desktop experience. Changes include:

- Reduce bottom margins and padding on mobile (mb-3 vs mb-6, px-2.5 vs px-4)
- Use responsive text sizes (text-xs sm:text-sm, text-base sm:text-xl)
- Add truncation and min-w-0 to prevent text overflow on small screens
- Hide non-essential info on mobile (token counts, keyboard shortcuts)
- Adjust gap spacing for tighter mobile layouts (gap-1.5 vs gap-3)
- Improve button touch targets with refined padding
- Update background colors for better contrast (gray-800 vs gray-900)
- Add border styling for enhanced component definition

Affects ClaudeStatus, CodeEditor, GitPanel, MainContent, MobileNav,
QuickSettingsPanel components and global styles. Ensures consistent
mobile-first design across the application.

src/components/QuickSettingsPanel.jsx

@@ -71,7 +71,7 @@ const QuickSettingsPanel = ({
 
       {/* Panel */}
       <div
-        className={`fixed top-0 right-0 h-full w-64 bg-white dark:bg-gray-900 border-l border-gray-200 dark:border-gray-700 shadow-xl transform transition-transform duration-150 ease-out z-40 ${
+        className={`fixed top-0 right-0 h-full w-64 bg-background border-l border-border shadow-xl transform transition-transform duration-150 ease-out z-40 ${
           localIsOpen ? 'translate-x-0' : 'translate-x-full'
         } ${isMobile ? 'h-screen' : ''}`}
       >
@@ -85,7 +85,7 @@ const QuickSettingsPanel = ({
           </div>
 
           {/* Settings Content */}
-          <div className={`flex-1 overflow-y-auto overflow-x-hidden p-4 space-y-6 bg-white dark:bg-gray-900 ${isMobile ? 'pb-mobile-nav' : ''}`}>
+          <div className={`flex-1 overflow-y-auto overflow-x-hidden p-4 space-y-6 bg-background ${isMobile ? 'pb-mobile-nav' : ''}`}>
             {/* Appearance Settings */}
             <div className="space-y-2">
               <h4 className="text-xs font-semibold uppercase tracking-wider text-gray-500 dark:text-gray-400 mb-2">Appearance</h4>