feat: PhotoPrism M0 bring-up — compose stack, web client, sidecar, migrate

Replace the legacy mule-image backend with PhotoPrism plus a thin
SvelteKit client and a Node sidecar for endpoints PhotoPrism doesn't
expose (file rename), and add a two-phase migrator (metadata via PUT,
heaps → albums) for the existing Postgres library.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/src/lib/queryClient.ts

@@ -0,0 +1,15 @@
+import { QueryClient } from '@tanstack/svelte-query';
+
+/**
+ * App-wide QueryClient singleton. `+layout.svelte` wires it into the
+ * provider; non-component code (Svelte actions, keyboard handlers) imports
+ * it directly to read cached photo state and invalidate after mutations.
+ */
+export const queryClient = new QueryClient({
+	defaultOptions: {
+		queries: {
+			staleTime: 30_000,
+			retry: 1
+		}
+	}
+});