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

app/map/page.tsx

@@ -0,0 +1,46 @@
+/**
+ * Map page — server component shell for the interactive map.
+ * Loads Leaflet CSS, renders the MapView client component.
+ */
+
+import { getConfig } from '@/lib/config';
+import { notFound } from 'next/navigation';
+import { MapView } from '@/components/MapView';
+import { BackLink } from '@/components/BackLink';
+import type { Metadata } from 'next';
+import './map.css';
+
+export const dynamic = 'force-dynamic';
+
+export const metadata: Metadata = {
+    title: 'Map',
+};
+
+export default function MapPage() {
+    const config = getConfig();
+
+    if (!config.map) {
+        notFound();
+    }
+
+    return (
+        <>
+            {/* Leaflet CSS from CDN */}
+            {/* eslint-disable-next-line @next/next/no-page-custom-font */}
+            <link
+                rel="stylesheet"
+                href="https://unpkg.com/leaflet@1.9.4/dist/leaflet.css"
+                integrity="sha256-p4NxAoJBhIIN+hmNHrzRCf9tD/miZyoHS5obTRR9BMY="
+                crossOrigin=""
+            />
+            <div className="map-page">
+                <div className="map-page__header">
+                    <BackLink href="/" label="Back to Gallery" />
+                    <h1 className="map-page__title">Map</h1>
+                    <p className="map-page__subtitle">Where the photos were taken</p>
+                </div>
+                <MapView />
+            </div>
+        </>
+    );
+}