feat(countries): replace Map view with browse-by-country (like Tags)

Removes the maplibre-gl Map view and adds "Countries" as a sixth
TagCategory, reusing the existing /tags/[category]/[[value]] browse
machinery instead of a bespoke map UI. Backed by a new self-contained
sidecar endpoint that aggregates photos.photo_country with BasePath
scoping, mirroring handleLabels/handleScopedCounts.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/lib/services/photoprism.ts

@@ -560,36 +560,19 @@ export async function listFolderCounts(paths: string[]): Promise<Record<string,
 	return out;
 }
 
-// ── Geo ──────────────────────────────────────────────────────────────────────
+// ── Countries ────────────────────────────────────────────────────────────────
 
-export interface PpGeoFeature {
-	type: 'Feature';
-	id: string;
-	geometry: { type: 'Point'; coordinates: [number, number] };
-	properties: {
-		UID: string;
-		Hash: string;
-		Title?: string;
-		TakenAt?: string;
-		FavId?: number;
-	};
+export interface PpCountry {
+	Code: string;
+	PhotoCount: number;
+	Thumb?: string;
 }
 
-export interface PpGeoCollection {
-	type: 'FeatureCollection';
-	features: PpGeoFeature[];
-	bbox?: number[];
-}
-
-export async function listGeo(q = ''): Promise<PpGeoCollection> {
-	// PhotoPrism's `/geo` returns a GeoJSON FeatureCollection of every
-	// matching geocoded photo. MapLibre's native clustering handles 50k+
-	// points without breaking a sweat (PhotoPrism upstream documents
-	// 500k); we ask for a generous cap that covers realistic libraries.
-	const { data } = await http.get<PpGeoCollection>('/geo', {
-		params: { count: 50000, q: q || undefined }
-	});
-
+export async function listCountries(): Promise<PpCountry[]> {
+	// Self-contained sidecar aggregation (groups photos.photo_country directly,
+	// no PhotoPrism proxy round-trip) so counts/thumbs are scoped to the
+	// caller's BasePath the same way /labels and /counts are.
+	const { data } = await sidecar.get<PpCountry[]>('/api/sidecar/countries');
 	return data;
 }