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/routers/__init__.py

@@ -11,6 +11,7 @@ from .users import router as users
 from .exchange import router as exchange
 from .marketplace_offers import router as marketplace_offers
 from .payments import router as payments
+from .web_vitals import router as web_vitals
 # from .registry import router as registry
 
-__all__ = ["client", "miner", "admin", "marketplace", "marketplace_gpu", "explorer", "services", "users", "exchange", "marketplace_offers", "payments", "registry"]
+__all__ = ["client", "miner", "admin", "marketplace", "marketplace_gpu", "explorer", "services", "users", "exchange", "marketplace_offers", "payments", "web_vitals", "registry"]

apps/coordinator-api/src/app/routers/web_vitals.py

@@ -0,0 +1,53 @@
+#!/usr/bin/env python3
+"""
+Web Vitals API endpoint for collecting performance metrics
+"""
+
+from fastapi import APIRouter, HTTPException
+from pydantic import BaseModel
+from typing import List, Dict, Any, Optional
+import logging
+
+router = APIRouter()
+
+class WebVitalsEntry(BaseModel):
+    name: str
+    startTime: Optional[float] = None
+    duration: Optional[float] = None
+
+class WebVitalsMetric(BaseModel):
+    name: str
+    value: float
+    id: str
+    delta: Optional[float] = None
+    entries: List[WebVitalsEntry] = []
+    url: Optional[str] = None
+    timestamp: Optional[str] = None
+
+@router.post("/web-vitals")
+async def collect_web_vitals(metric: WebVitalsMetric):
+    """
+    Collect Web Vitals performance metrics from the frontend.
+    This endpoint receives Core Web Vitals (LCP, FID, CLS, TTFB, FCP) for monitoring.
+    """
+    try:
+        # Log the metric for monitoring/analysis
+        logging.info(f"Web Vitals - {metric.name}: {metric.value}ms (ID: {metric.id}) from {metric.url or 'unknown'}")
+        
+        # In a production setup, you might:
+        # - Store in database for trend analysis
+        # - Send to monitoring service (DataDog, New Relic, etc.)
+        # - Trigger alerts for poor performance
+        
+        # For now, just acknowledge receipt
+        return {"status": "received", "metric": metric.name, "value": metric.value}
+        
+    except Exception as e:
+        logging.error(f"Error processing web vitals metric: {e}")
+        raise HTTPException(status_code=500, detail="Failed to process metric")
+
+# Health check for web vitals endpoint
+@router.get("/web-vitals/health")
+async def web_vitals_health():
+    """Health check for web vitals collection endpoint"""
+    return {"status": "healthy", "service": "web-vitals"}