feat(database): make token column nullable in caldav_tokens table for improved flexibility

server/routes/calendar.js

@@ -752,7 +752,7 @@ router.post('/caldav-tokens', authenticateToken, async (req, res) => {
     const tokenHash = crypto.createHash('sha256').update(token).digest('hex');
     const result = await db.run(
       // Store only the hash — never the plaintext — to limit exposure on DB breach.
-      'INSERT INTO caldav_tokens (user_id, token, token_hash, name) VALUES (?, NULL, ?, ?)',
+      'INSERT INTO caldav_tokens (user_id, token_hash, name) VALUES (?, ?, ?)',
       [req.user.id, tokenHash, name.trim()],
     );
     res.status(201).json({