feat: Add theme system with 7 themes including Otaku and Pink Pink

- Implement ThemeContext with CSS variables for dynamic theming
- Add theme presets: Cyberpunk, Windows Classic, Dark Modern, Matrix, Industrial, Otaku Mode, Pink Pink
- Add theme selector UI in Footer with color preview
- Theme persists to localStorage
- Each theme has unique background effects, colors, and styling
- Otaku Mode: anime-style dark purple with pink/purple glow and star effects
- Pink Pink: cute pastel pink with heart pattern overlay

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

FrontEnd/App.tsx

@@ -8,6 +8,7 @@ import { HistoryPage } from './pages/HistoryPage';
 import { SystemState, Recipe, IOPoint, LogEntry, RobotTarget, ConfigItem } from './types';
 import { comms } from './communication';
 import { AlertProvider, useAlert } from './contexts/AlertContext';
+import { ThemeProvider } from './contexts/ThemeContext';
 import { PickerMoveDialog } from './components/PickerMoveDialog';
 
 // PickerMoveDialog 전역 상태 Context
@@ -329,11 +330,13 @@ function AppContent() {
   );
 }
 
-// 외부 App 컴포넌트 - AlertProvider로 감싸기
+// 외부 App 컴포넌트 - ThemeProvider + AlertProvider로 감싸기
 export default function App() {
   return (
-    <AlertProvider>
-      <AppContent />
-    </AlertProvider>
+    <ThemeProvider>
+      <AlertProvider>
+        <AppContent />
+      </AlertProvider>
+    </ThemeProvider>
   );
 }