Seed household on container startup via seed.mjs

Without a household row the signIn callback has nothing to attach the
first user to, causing "No household membership" on first load. Add
scripts/seed.mjs (plain ESM, only needs postgres which is already in the
image) and run it from the entrypoint after migrations. Idempotent — skips
if a household already exists. Default calendars/lists are created by the
signIn callback when the first user authenticates.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/seed.mjs

@@ -0,0 +1,24 @@
+import postgres from "postgres";
+
+const url = process.env.DATABASE_URL;
+if (!url) {
+  console.error(JSON.stringify({ level: "error", msg: "DATABASE_URL is required" }));
+  process.exit(1);
+}
+
+const sql = postgres(url, { max: 1 });
+
+try {
+  const [existing] = await sql`SELECT id, name FROM households LIMIT 1`;
+  if (existing) {
+    console.log(JSON.stringify({ level: "info", msg: "household exists", name: existing.name }));
+  } else {
+    await sql`INSERT INTO households (name) VALUES ('Home')`;
+    console.log(JSON.stringify({ level: "info", msg: "seeded household Home" }));
+  }
+} catch (err) {
+  console.error(JSON.stringify({ level: "error", msg: "seed failed", err: String(err) }));
+  process.exit(1);
+} finally {
+  await sql.end({ timeout: 5 });
+}