feat: pairs answer_type TEXT[], statements.answer bool

- pairs: answer_type changed from VARCHAR(20) to TEXT[] (multi-value)
  POST/PATCH now accept arrays like ['text','yes_no','word']
- statements: add answer BOOLEAN (nullable) for yes/no correct answer
- migration: ALTER TABLE pairs + ADD COLUMN statements.answer

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

src/db-migrate.js

@@ -319,6 +319,16 @@ async function migrate() {
     )
   `);
 
+  // pairs.answer_type → TEXT[] (multi-select)
+  await query(`ALTER TABLE pairs DROP CONSTRAINT IF EXISTS pairs_answer_type_check`).catch(() => {});
+  await query(`
+    ALTER TABLE pairs ALTER COLUMN answer_type TYPE TEXT[]
+    USING ARRAY[answer_type]::TEXT[]
+  `).catch(() => {});
+
+  // statements.answer — boolean nullable (for yes/no correct answer)
+  await query(`ALTER TABLE statements ADD COLUMN IF NOT EXISTS answer BOOLEAN`);
+
   // 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`);

src/routes/pairs.js

@@ -2,7 +2,14 @@ const router = require('express').Router();
 const { query } = require('../db');
 
 const STATUSES = ['draft', 'blocked', 'published'];
-const ANSWER_TYPES = ['yes_no', 'text', 'word'];
+const ANSWER_TYPES = new Set(['yes_no', 'text', 'word']);
+
+function validateAnswerType(val) {
+  const arr = Array.isArray(val) ? val : (val ? [val] : []);
+  if (!arr.length) return 'answer_type must be a non-empty array of: yes_no, text, word';
+  if (!arr.every(t => ANSWER_TYPES.has(t))) return `answer_type values must be: ${[...ANSWER_TYPES].join(', ')}`;
+  return null;
+}
 
 const STATUS_TIMESTAMP = {
   published: 'published_at',
@@ -41,14 +48,15 @@ router.post('/', async (req, res, next) => {
     const { answer_type, difficulty_level, question_id,
             positive_statement_id, negative_statement_id, blocked_topic } = req.body;
 
-    if (!answer_type || !ANSWER_TYPES.includes(answer_type))
+    const atErr = validateAnswerType(answer_type);
-      return res.status(400).json({ error: `answer_type required, must be one of: ${ANSWER_TYPES.join(', ')}` });
+    if (atErr) return res.status(400).json({ error: atErr });
+    const atArr = Array.isArray(answer_type) ? answer_type : [answer_type];
 
     const result = await query(
       `INSERT INTO pairs
          (answer_type, difficulty_level, question_id, positive_statement_id, negative_statement_id, blocked_topic)
        VALUES ($1, $2, $3, $4, $5, $6) RETURNING *`,
-      [answer_type, difficulty_level || null, question_id || null,
+      [atArr, difficulty_level || null, question_id || null,
        positive_statement_id || null, negative_statement_id || null, blocked_topic || null]
     );
     res.status(201).json(result.rows[0]);

src/routes/statements.js

@@ -58,16 +58,17 @@ router.post('/', async (req, res, next) => {
     const {
       negative_sentence_de, negative_sentence_en, negative_sentence_sv,
       positive_sentence_de, positive_sentence_en, positive_sentence_sv,
-      blocked_topic,
+      blocked_topic, answer,
     } = req.body;
     const result = await query(
       `INSERT INTO statements
          (negative_sentence_de, negative_sentence_en, negative_sentence_sv,
-          positive_sentence_de, positive_sentence_en, positive_sentence_sv, blocked_topic)
+          positive_sentence_de, positive_sentence_en, positive_sentence_sv,
-       VALUES ($1,$2,$3,$4,$5,$6,$7) RETURNING *`,
+          blocked_topic, answer)
+       VALUES ($1,$2,$3,$4,$5,$6,$7,$8) RETURNING *`,
       [negative_sentence_de || null, negative_sentence_en || null, negative_sentence_sv || null,
        positive_sentence_de || null, positive_sentence_en || null, positive_sentence_sv || null,
-       blocked_topic || null]
+       blocked_topic || null, answer !== undefined ? answer : null]
     );
     res.status(201).json({ ...result.rows[0], positive_word_ids: [], negative_word_ids: [] });
   } catch (err) { next(err); }
@@ -78,7 +79,8 @@ router.patch('/:id', async (req, res, next) => {
   try {
     const allowed = ['status', 'blocked_topic', 'published_at', 'blocked_at',
                      'negative_sentence_de', 'negative_sentence_en', 'negative_sentence_sv',
-                     'positive_sentence_de', 'positive_sentence_en', 'positive_sentence_sv'];
+                     'positive_sentence_de', 'positive_sentence_en', 'positive_sentence_sv',
+                     'answer'];
     const fields = Object.keys(req.body).filter(k => allowed.includes(k));
     if (!fields.length) return res.status(400).json({ error: 'No valid fields provided' });