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

apps/coordinator-api/src/app/main.py

@@ -19,6 +19,7 @@ from .routers import (
     zk_applications,
     explorer,
     payments,
+    web_vitals,
 )
 from .routers.governance import router as governance
 from .routers.partners import router as partners
@@ -75,6 +76,7 @@ def create_app() -> FastAPI:
     app.include_router(governance, prefix="/v1")
     app.include_router(partners, prefix="/v1")
     app.include_router(explorer, prefix="/v1")
+    app.include_router(web_vitals, prefix="/v1")
 
     # Add Prometheus metrics endpoint
     metrics_app = make_asgi_app()