feat: add smart map view with location-level clustering

- /map page with Leaflet (CartoDB dark tiles)
- Photos clustered by city/country (not per-photo)
- /api/map endpoint with encrypted cover asset IDs
- Configurable via gallery.yaml (map: true/false)
- Conditional nav link in header
- CSP updated for Leaflet CDN and tile servers
- Theme-aware popups with cover thumbnails and album links

next.config.ts

@@ -5,9 +5,9 @@ import type { NextConfig } from 'next';
 const cspDirectives = [
   "default-src 'self'",
   "script-src 'self' 'unsafe-inline'",
-  "style-src 'self' 'unsafe-inline' https://fonts.googleapis.com",
+  "style-src 'self' 'unsafe-inline' https://fonts.googleapis.com https://unpkg.com",
   "font-src 'self' https://fonts.gstatic.com",
-  "img-src 'self' data:",
+  "img-src 'self' data: https://*.basemaps.cartocdn.com",
   "connect-src 'self'",
   "frame-ancestors 'none'",
   "base-uri 'self'",