feat(client): add routing and sidebar icons

- install react-router-dom and wrap app in HashRouter to avoid dev proxy conflicts
- replace useState-based section switching with NavLink + Routes
- add lucide icons (Globe, KeyRound, Monitor, ClipboardList) to nav items
- icon opacity transitions on hover and active state via CSS

client/package.json

@@ -15,7 +15,8 @@
     "lucide-react": "^1.7.0",
     "react": "^19.1.0",
     "react-dom": "^19.1.0",
-    "react-i18next": "^17.0.2"
+    "react-i18next": "^17.0.2",
+    "react-router-dom": "^7.14.0"
   },
   "devDependencies": {
     "@storybook/addon-a11y": "^10.3.5",