feat: words table, M2M with pictures and categories

- words table with trilingual titles, status enum, difficulty level, timestamps
- word_pictures junction table (M2M words <-> pictures)
- categories placeholder table
- word_categories junction table (M2M words <-> categories)
- Auto-timestamps on status change (requested/published/blocked)
- Full CRUD + link/unlink endpoints for pictures and categories
- README updated with schema and endpoints

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

src/db-migrate.js

@@ -34,7 +34,66 @@ async function migrate() {
       FOR EACH ROW EXECUTE FUNCTION update_updated_at()
   `);
 
-  console.log('Migration complete: pictures table ready');
+  // words
+  await query(`
+    CREATE TABLE IF NOT EXISTS words (
+      id                UUID        PRIMARY KEY DEFAULT gen_random_uuid(),
+      titel_de          TEXT,
+      titel_en          TEXT,
+      titel_se          TEXT,
+      status            VARCHAR(20) NOT NULL DEFAULT 'requested'
+                          CHECK (status IN ('requested', 'translated', 'generated', 'blocked', 'published')),
+      difficulty_level  SMALLINT    CHECK (difficulty_level BETWEEN 1 AND 50),
+      requested_at      TIMESTAMPTZ,
+      published_at      TIMESTAMPTZ,
+      blocked_at        TIMESTAMPTZ,
+      created_at        TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+      updated_at        TIMESTAMPTZ NOT NULL DEFAULT NOW()
+    )
+  `);
+
+  await query(`
+    DROP TRIGGER IF EXISTS words_updated_at ON words;
+    CREATE TRIGGER words_updated_at
+      BEFORE UPDATE ON words
+      FOR EACH ROW EXECUTE FUNCTION update_updated_at()
+  `);
+
+  // M2M: words <-> pictures
+  await query(`
+    CREATE TABLE IF NOT EXISTS word_pictures (
+      word_id     UUID NOT NULL REFERENCES words(id) ON DELETE CASCADE,
+      picture_id  UUID NOT NULL REFERENCES pictures(id) ON DELETE CASCADE,
+      PRIMARY KEY (word_id, picture_id)
+    )
+  `);
+
+  // categories (Platzhalter — Felder folgen im nächsten Schritt)
+  await query(`
+    CREATE TABLE IF NOT EXISTS categories (
+      id         UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+      created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+      updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+    )
+  `);
+
+  await query(`
+    DROP TRIGGER IF EXISTS categories_updated_at ON categories;
+    CREATE TRIGGER categories_updated_at
+      BEFORE UPDATE ON categories
+      FOR EACH ROW EXECUTE FUNCTION update_updated_at()
+  `);
+
+  // M2M: words <-> categories
+  await query(`
+    CREATE TABLE IF NOT EXISTS word_categories (
+      word_id     UUID NOT NULL REFERENCES words(id) ON DELETE CASCADE,
+      category_id UUID NOT NULL REFERENCES categories(id) ON DELETE CASCADE,
+      PRIMARY KEY (word_id, category_id)
+    )
+  `);
+
+  console.log('Migration complete');
 }
 
 module.exports = migrate;