feat(housekeeping): add per-hotel theme manager with import/export and background

Theme Manager under /admin-next/hotel/theme-manager lets the owner save, apply, rename, delete, import, and export custom themes, plus set a custom site background by URL or upload. Themes are stored in WebsiteSetting/custom_themes JSON so they survive CMS updates.

src/features/housekeeping/foundation/registry.test.ts

@@ -166,6 +166,15 @@ const expectedManifests = [
 			PERMS.CATALOG_EDIT,
 		],
 		routes: [
+			{
+				id: "theme-manager",
+				labelKey: "pages.housekeeping.domains.hotel.routes.themeManager",
+				href: "/admin-next/hotel/theme-manager",
+				capability: {
+					mode: "any",
+					slugs: [PERMS.SETTINGS_VIEW, PERMS.SETTINGS_EDIT],
+				},
+			},
 			{
 				id: "nitro-cleanup",
 				labelKey: "pages.housekeeping.domains.hotel.routes.nitroCleanup",