feat(web): re-apply dashboard UI improvements on top of i18n

Re-applies changes from #9471 that were overwritten by the i18n PR:

- URL-based routing via react-router-dom (NavLink, Routes, BrowserRouter)
- Replace emoji icons with lucide-react in ConfigPage and SkillsPage
- Sidebar layout for ConfigPage, SkillsPage, and LogsPage
- Custom dropdown Select component (SelectOption) in CronPage
- Remove all non-functional rounded borders across the UI
- Fixed header with proper content offset

Made-with: Cursor

web/src/components/OAuthProvidersCard.tsx

@@ -171,7 +171,7 @@ export function OAuthProvidersCard({ onError, onSuccess }: Props) {
                     {!p.status.logged_in && (
                       <span className="text-xs text-muted-foreground/80">
                         {t.oauth.notConnected.split("{command}")[0]}
-                        <code className="text-foreground bg-secondary/40 px-1 rounded">
+                        <code className="text-foreground bg-secondary/40 px-1">
                           {p.cli_command}
                         </code>
                         {t.oauth.notConnected.split("{command}")[1]}