feat: add dark mode, navigation, and Web Vitals tracking to marketplace

Backend:
- Simplify DatabaseConfig: remove effective_url property and project root finder
- Update to Pydantic v2 model_config (replace nested Config class)
- Add web_vitals router to main.py and __init__.py
- Fix ExplorerService datetime handling (ensure timezone-naive comparisons)
- Fix status_label extraction to handle both enum and string job states

Frontend (Marketplace):
- Add dark mode toggle with system preference detection

website/docs/miners.html

@@ -315,7 +315,7 @@ nano ~/.aitbc/miner.toml</div>
                     <li>Check the logs: <code>./aitbc-miner logs</code></li>
                     <li>Visit our Discord community</li>
                     <li>Search issues on Gitea</li>
-                    <li>Email support: aitbc@bubuit.net</li>
+                    <li>Email support: andreas.fleckl@bubuit.net</li>
                 </ul>
             </section>