feat: TTS-Settings je Sprache, Audio-Coverage entkoppelt, Veröffentlichen-Workflow

- tts_settings (voice/model/speed/... pro Sprache) + Seed de/en/sv; Route /api/tts-settings
- audios: Stimme/Parameter aus tts_settings; Coverage zählt jetzt auch draft/translated
- pairs: GET /publishability (Readiness, sortierbar nach 'am wenigsten fehlt'),
  POST /:id/publish (kaskadiert question/statements→published, validiert Bild+Audio je Sprache)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/db-migrate.js

@@ -572,6 +572,34 @@ async function migrate() {
       FOR EACH ROW EXECUTE FUNCTION update_updated_at()
   `);
 
+  // tts_settings — Stimme + Parameter pro Sprache (zentral konfigurierbar)
+  await query(`
+    CREATE TABLE IF NOT EXISTS tts_settings (
+      language          VARCHAR(10) PRIMARY KEY,
+      voice_id          TEXT        NOT NULL,
+      model_id          TEXT        NOT NULL DEFAULT 'eleven_multilingual_v2',
+      speed             NUMERIC(4,2) NOT NULL DEFAULT 1.0,
+      stability         NUMERIC(4,2) NOT NULL DEFAULT 0.5,
+      similarity_boost  NUMERIC(4,2) NOT NULL DEFAULT 0.75,
+      style             NUMERIC(4,2) NOT NULL DEFAULT 0.0,
+      updated_at        TIMESTAMPTZ NOT NULL DEFAULT NOW()
+    )
+  `);
+  await query(`
+    DROP TRIGGER IF EXISTS tts_settings_updated_at ON tts_settings;
+    CREATE TRIGGER tts_settings_updated_at
+      BEFORE UPDATE ON tts_settings
+      FOR EACH ROW EXECUTE FUNCTION update_updated_at()
+  `);
+  // Seed-Stimmen (nur einfügen wenn fehlt — manuelle Änderungen bleiben erhalten)
+  await query(`
+    INSERT INTO tts_settings (language, voice_id) VALUES
+      ('de', 'rKiu7lQ4c5P3az3745s3'),
+      ('en', 'cVd39cx0VtXNC13y5Y7z'),
+      ('sv', 'XXCqsM8I9KhqA7jLGj1U')
+    ON CONFLICT (language) DO NOTHING
+  `).catch(() => {});
+
   // ── Migrate old {{uuid}} placeholders → new {{label.w:uuid}} / {{label.o:uuid}} ──
   await migratePlaceholders();