feat: objects_created flag on pictures, native_lang on users

- pictures: add objects_created (bool) + objects_created_at (auto timestamp)
  GET /pictures supports ?objects_created=true/false filter
  PATCH /pictures/:id allows setting objects_created
- db-migrate: seed German language, link to all existing users
- auth/login: include native_lang (from languages table) in response + JWT

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

src/db-migrate.js

@@ -319,6 +319,26 @@ async function migrate() {
     )
   `);
 
+  // objects_created on pictures
+  await query(`ALTER TABLE pictures ADD COLUMN IF NOT EXISTS objects_created BOOLEAN NOT NULL DEFAULT false`);
+  await query(`ALTER TABLE pictures ADD COLUMN IF NOT EXISTS objects_created_at TIMESTAMPTZ`);
+
+  // language_native_id on users
+  await query(`ALTER TABLE users ADD COLUMN IF NOT EXISTS language_native_id UUID REFERENCES languages(id) ON DELETE SET NULL`);
+
+  // Seed German language (idempotent)
+  await query(`
+    INSERT INTO languages (titel_en, titel_de, titel_sv, short_en, status)
+    SELECT 'German', 'Deutsch', 'Tyska', 'de', 'published'
+    WHERE NOT EXISTS (SELECT 1 FROM languages WHERE short_en = 'de')
+  `);
+
+  // Set all users without a native language to German
+  await query(`
+    UPDATE users SET language_native_id = (SELECT id FROM languages WHERE short_en = 'de' LIMIT 1)
+    WHERE language_native_id IS NULL
+  `);
+
   // blocklist
   await query(`
     CREATE TABLE IF NOT EXISTS blocklist (