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>

migrate/legacy_export.mjs

@@ -0,0 +1,90 @@
+#!/usr/bin/env node
+// Dumps a legacy mule-image Postgres into the snapshot JSON shape `run.mjs`
+// consumes. Intended to run on the homecloud server where the legacy stack
+// lives (since `DATABASE_URL` points at the in-network Postgres there).
+//
+//   DATABASE_URL=postgres://mulita:mulita@db:5432/mulita \
+//   node migrate/legacy_export.mjs > snapshot.json
+//
+// Uses the `pg` npm package which the legacy mule-image already ships in
+// its backend image; if you're running this from a separate workstation,
+// `npm install pg` first.
+
+import pg from 'pg';
+import process from 'node:process';
+
+const DATABASE_URL = process.env.DATABASE_URL;
+if (!DATABASE_URL) {
+	console.error('DATABASE_URL required');
+	process.exit(2);
+}
+
+const client = new pg.Client({ connectionString: DATABASE_URL });
+await client.connect();
+
+// ── photos ───────────────────────────────────────────────────────────────────
+
+// Mule-image's photos table is the source of all per-file metadata. The
+// migrator only reads fields that have a clean PhotoPrism mapping; the
+// rest (auto-tags, ML-derived fields, etc.) are skipped per the merge plan.
+const photoRows = await client.query(`
+	SELECT
+	  p.filepath,
+	  p.user_title,
+	  p.user_notes,
+	  p.rating,
+	  p.is_picked,
+	  p.is_discarded,
+	  p.is_hidden,
+	  p.taken_at,
+	  COALESCE(
+	    array_agg(t.name) FILTER (WHERE t.name IS NOT NULL),
+	    '{}'
+	  ) AS tags
+	FROM photos p
+	LEFT JOIN photo_tags pt ON pt.photo_id = p.id
+	LEFT JOIN tags t ON t.id = pt.tag_id
+	WHERE p.is_active IS NULL OR p.is_active = true
+	GROUP BY p.id
+`);
+
+// ── heaps + memberships ─────────────────────────────────────────────────────
+
+const heapRows = await client.query(`
+	SELECT h.id, h.name FROM heaps h WHERE h.is_active = true
+`);
+
+const heapMembers = await client.query(`
+	SELECT hp.heap_id, p.filepath
+	FROM heap_photos hp
+	JOIN photos p ON p.id = hp.photo_id
+`);
+
+const membersByHeap = new Map();
+for (const r of heapMembers.rows) {
+	if (!membersByHeap.has(r.heap_id)) membersByHeap.set(r.heap_id, []);
+	membersByHeap.get(r.heap_id).push(r.filepath);
+}
+
+// ── assemble ─────────────────────────────────────────────────────────────────
+
+const snapshot = {
+	photos: photoRows.rows.map((r) => ({
+		filepath: r.filepath,
+		user_title: r.user_title,
+		user_notes: r.user_notes,
+		rating: r.rating,
+		is_picked: Boolean(r.is_picked),
+		is_discarded: Boolean(r.is_discarded),
+		is_hidden: Boolean(r.is_hidden),
+		taken_at: r.taken_at ? new Date(r.taken_at).toISOString() : null,
+		tags: r.tags ?? []
+	})),
+	heaps: heapRows.rows.map((h) => ({
+		name: h.name,
+		photo_filepaths: membersByHeap.get(h.id) ?? []
+	}))
+};
+
+process.stdout.write(JSON.stringify(snapshot, null, 2));
+await client.end();