feat(frontend): port Places, People & photo tabs to the Svelte app

Bring the Photos/People/Places UI that main added (in the legacy vanilla
frontend) into the SvelteKit rewrite, wired to the now-merged backend
(/api/photos/geo, /api/people/*).

Photos page (routes/photos/+page.svelte):
- Moments | Places | People sub-tabs (the People tab appears only when the
  faces feature is enabled, via a /api/people capability probe), mirroring
  the vanilla photos sub-nav.
- Square ↔ justified layout toggle. Justified uses a Flickr-style
  row-packer over the width/height the photos list endpoint returns
  (PhotoItem), falling back to 1:1 when dimensions are missing.

New components:
- PhotoLightbox.svelte — the lightbox extracted from the photos page into a
  reusable component (items + bindable index, onDelete callback) so the
  grid, People and Places all share one implementation (no duplication).
- PlacesMap.svelte — MapLibre GL map with server-clustered markers; the
  vector basemap is optional (probed at /basemaps/basemap.pmtiles, themed
  fallback otherwise). Cluster click zooms in or opens the lightbox.
- PeopleView.svelte — identity-cluster grid → per-person photo grid, with
  rename via the in-app prompt dialog.

Supporting:
- api/endpoints/people.ts (+ peopleEnabled probe); photos.ts gains
  fetchPhotosGeo + GeoCluster + PhotoItem; fileThumbnailUrl takes a size.
- lib/vendor/maplibre.ts — minimal typings + lazy loader for the vendored
  MapLibre GL + pmtiles globals (kept any-free for ESLint).
- utils/media.ts — shared isVideo / photoTimestamp / minimalPhotoItem.
- Vendored maplibre-gl 5.24.0 + pmtiles 4.4.1 under static/vendors and an
  optional static/basemaps dir, matching the PR's vendored-asset pattern.
- New photos.tab_*/layout_*/map_* + people.* keys in en.json.

Verified: npm run check (svelte-check + eslint + stylelint + prettier),
npm run test:unit (36 pass), and npm run build all green.

frontend/src/lib/vendor/maplibre.ts

@@ -0,0 +1,95 @@
+/**
+ * Minimal typings + lazy loader for the vendored MapLibre GL + pmtiles globals.
+ *
+ * The libraries are heavy (~1 MB) and only the Places map needs them, so they
+ * are vendored under `/vendors` (not bundled) and injected on first use — the
+ * same pattern the legacy frontend used. We declare only the small slice of the
+ * MapLibre API the Places view touches, so the rest of the app stays `any`-free.
+ */
+
+export interface MapBounds {
+	getWest(): number;
+	getSouth(): number;
+	getEast(): number;
+	getNorth(): number;
+}
+
+export interface LngLatBounds {
+	extend(lngLat: [number, number]): LngLatBounds;
+	isEmpty(): boolean;
+}
+
+export interface MapMarker {
+	setLngLat(lngLat: [number, number]): MapMarker;
+	addTo(map: MapLibreMap): MapMarker;
+	remove(): void;
+}
+
+export interface MapLibreMap {
+	addControl(control: unknown, position?: string): MapLibreMap;
+	on(type: string, listener: () => void): void;
+	getBounds(): MapBounds;
+	getZoom(): number;
+	resize(): void;
+	easeTo(opts: { center: [number, number]; zoom: number }): void;
+	fitBounds(
+		bounds: LngLatBounds,
+		opts?: { padding?: number; maxZoom?: number; duration?: number }
+	): void;
+	remove(): void;
+}
+
+export interface MapLibreModule {
+	Map: new (opts: Record<string, unknown>) => MapLibreMap;
+	Marker: new (opts: { element: HTMLElement }) => MapMarker;
+	NavigationControl: new (opts?: { showCompass?: boolean }) => unknown;
+	AttributionControl: new (opts?: { customAttribution?: string }) => unknown;
+	LngLatBounds: new () => LngLatBounds;
+	addProtocol(name: string, fn: unknown): void;
+}
+
+export interface PMTilesModule {
+	Protocol: new () => { tile: unknown };
+}
+
+export interface MapLibs {
+	maplibregl: MapLibreModule;
+	pmtiles: PMTilesModule;
+}
+
+let cached: MapLibs | null = null;
+
+/** Inject a vendored script once, resolving when it has loaded. */
+function loadScript(src: string): Promise<void> {
+	return new Promise((resolve, reject) => {
+		if (document.querySelector(`script[data-vendor="${src}"]`)) {
+			resolve();
+			return;
+		}
+		const s = document.createElement('script');
+		s.src = src;
+		s.async = true;
+		s.dataset.vendor = src;
+		s.addEventListener('load', () => resolve());
+		s.addEventListener('error', () => reject(new Error(`Failed to load ${src}`)));
+		document.head.appendChild(s);
+	});
+}
+
+/** Lazy-load MapLibre GL + pmtiles.js (+ MapLibre CSS) and read their globals. */
+export async function loadMapLibs(): Promise<MapLibs> {
+	if (cached) return cached;
+	if (!document.querySelector('link[data-vendor="maplibre-css"]')) {
+		const l = document.createElement('link');
+		l.rel = 'stylesheet';
+		l.href = '/vendors/maplibre-gl.css';
+		l.dataset.vendor = 'maplibre-css';
+		document.head.appendChild(l);
+	}
+	await loadScript('/vendors/maplibre-gl.js');
+	await loadScript('/vendors/pmtiles.js');
+	const w = window as unknown as { maplibregl?: MapLibreModule; pmtiles?: PMTilesModule };
+	if (!w.maplibregl || !w.pmtiles) throw new Error('map libraries failed to initialise');
+	cached = { maplibregl: w.maplibregl, pmtiles: w.pmtiles };
+	return cached;
+}