feat: Implement internationalization with react-i18next, add translation files, and integrate language switching across components.

k-notes-frontend/package.json

@@ -50,6 +50,10 @@
     "cmdk": "^1.1.1",
     "date-fns": "^4.1.0",
     "embla-carousel-react": "^8.6.0",
+    "i18next": "^25.7.3",
+    "i18next-browser-languagedetector": "^8.2.0",
+    "i18next-cli": "^1.33.5",
+    "i18next-http-backend": "^3.0.2",
     "idb": "^8.0.3",
     "input-otp": "^1.4.2",
     "lucide-react": "^0.562.0",
@@ -58,6 +62,7 @@
     "react-day-picker": "^9.13.0",
     "react-dom": "^19.2.0",
     "react-hook-form": "^7.69.0",
+    "react-i18next": "^16.5.0",
     "react-markdown": "^10.1.0",
     "react-masonry-css": "^1.0.16",
     "react-resizable-panels": "^4.0.15",