feat: auth route uses named admin lookup, embeds name in JWT

- Login/verify use findAdminByKey; JWT and response include admin name
- Verify returns 403 when token lacks name (legacy tokens)
- Test tokens include name for getAuthToken()
- Set Content-Type on supertest JSON bodies (superagent/mime resolution)

Made-with: Cursor

tests/helpers/test-utils.js

@@ -2,7 +2,7 @@ const jwt = require('jsonwebtoken');
 const db = require('../../backend/database');
 
 function getAuthToken() {
-  return jwt.sign({ role: 'admin' }, process.env.JWT_SECRET, { expiresIn: '1h' });
+  return jwt.sign({ role: 'admin', name: 'TestAdmin' }, process.env.JWT_SECRET, { expiresIn: '1h' });
 }
 
 function getAuthHeader() {