Add languages, user_names, users_public tables and routes; fix _se→_sv rename

- Fix broken rename migration array (sed had corrupted from values to _sv)
- Add languages table with status lifecycle and trilingual titles
- Add user_names table with unique lowercase index
- Add users_public table linking to user_names and languages (native/target)
- Wire all three new routes under /api/languages, /api/user-names, /api/users-public

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

src/routes/user-names.js

@@ -0,0 +1,67 @@
+const router = require('express').Router();
+const { query } = require('../db');
+
+// GET /api/user-names
+router.get('/', async (req, res, next) => {
+  try {
+    const { limit = 50, offset = 0 } = req.query;
+    const result = await query(
+      `SELECT * FROM user_names ORDER BY created_at DESC LIMIT $1 OFFSET $2`,
+      [Math.min(parseInt(limit), 500), parseInt(offset)]
+    );
+    res.json(result.rows);
+  } catch (err) { next(err); }
+});
+
+// GET /api/user-names/:id
+router.get('/:id', async (req, res, next) => {
+  try {
+    const result = await query('SELECT * FROM user_names WHERE id = $1', [req.params.id]);
+    if (!result.rows.length) return res.status(404).json({ error: 'Not found' });
+    res.json(result.rows[0]);
+  } catch (err) { next(err); }
+});
+
+// POST /api/user-names
+router.post('/', async (req, res, next) => {
+  try {
+    const { username } = req.body;
+    if (!username) return res.status(400).json({ error: 'username is required' });
+    const result = await query(
+      `INSERT INTO user_names (username, username_lowercase) VALUES ($1, $2) RETURNING *`,
+      [username, username.toLowerCase()]
+    );
+    res.status(201).json(result.rows[0]);
+  } catch (err) {
+    if (err.code === '23505') return res.status(409).json({ error: 'Username already taken' });
+    next(err);
+  }
+});
+
+// PATCH /api/user-names/:id
+router.patch('/:id', async (req, res, next) => {
+  try {
+    const { username } = req.body;
+    if (!username) return res.status(400).json({ error: 'No valid fields provided' });
+    const result = await query(
+      `UPDATE user_names SET username = $1, username_lowercase = $2 WHERE id = $3 RETURNING *`,
+      [username, username.toLowerCase(), req.params.id]
+    );
+    if (!result.rows.length) return res.status(404).json({ error: 'Not found' });
+    res.json(result.rows[0]);
+  } catch (err) {
+    if (err.code === '23505') return res.status(409).json({ error: 'Username already taken' });
+    next(err);
+  }
+});
+
+// DELETE /api/user-names/:id
+router.delete('/:id', async (req, res, next) => {
+  try {
+    const result = await query('DELETE FROM user_names WHERE id = $1 RETURNING id', [req.params.id]);
+    if (!result.rows.length) return res.status(404).json({ error: 'Not found' });
+    res.status(204).end();
+  } catch (err) { next(err); }
+});
+
+module.exports = router;