Improve overall user interface and fix reported functionality problems

Fixes dark mode toggle, landing page layout, dashboard structure, and removes unused imports.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: d7e7c4e8-20cb-41c4-9d0e-79f48938fede
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/9777c70b-fc38-4831-8d6b-78dfffe041b0/d4eed189-5f49-4ca5-967b-42e14b879685.jpg

client/src/pages/SettingsPage.tsx

@@ -243,7 +243,20 @@ export default function SettingsPage() {
                         Switch between light and dark themes
                       </p>
                     </div>
-                    <Switch />
+                    <Switch 
+                      checked={theme === 'dark'}
+                      onCheckedChange={toggleTheme}
+                    />
+                  </div>
+                  <Separator />
+                  <div className="space-y-4">
+                    <div>
+                      <Label>Language</Label>
+                      <p className="text-sm text-gray-600 dark:text-gray-400 mb-2">
+                        Choose your preferred language
+                      </p>
+                      <LanguageSwitcher />
+                    </div>
                   </div>
                 </CardContent>
               </Card>