feat: add Korean-English localization and light theme

Localize studio, curriculum, visualization and loading interfaces. Add persistent language and theme settings, refine module loading states, and normalize remote shell locales.

package.json

@@ -8,6 +8,8 @@
     "email": "hooladhoon@gmail.com"
   },
   "scripts": {
+    "test:i18n": "node --test scripts/test-i18n.cjs",
+    "test:theme": "node --test scripts/test-studio-theme.cjs",
     "dev": "electron-vite dev",
     "build": "electron-vite build",
     "build:linux": "npm run build && electron-builder --linux"
@@ -55,9 +57,11 @@
     "@xterm/addon-fit": "^0.11.0",
     "@xterm/xterm": "^6.0.0",
     "driver.js": "^1.4.0",
+    "i18next": "^26.4.2",
     "lucide-react": "^1.14.0",
     "monaco-editor": "^0.55.1",
     "node-pty": "^1.1.0",
+    "react-i18next": "^17.0.15",
     "react-markdown": "^10.1.0",
     "remark-gfm": "^4.0.1",
     "socket.io-client": "^4.8.3",