feat: add tbank tokens

src/tbank/tbank.crypto.spec.ts

@@ -0,0 +1,16 @@
+import { TbankCrypto } from './tbank.crypto';
+
+describe('TbankCrypto', () => {
+  it('round-trips a token and rejects a malformed key', () => {
+    const crypto = TbankCrypto.fromBase64(
+      'MDEyMzQ1Njc4OWFiY2RlZjAxMjM0NTY3ODlhYmNkZWY=',
+    );
+    const encrypted = crypto.encrypt('secret-token');
+
+    expect(encrypted).not.toContain('secret-token');
+    expect(crypto.decrypt(encrypted)).toBe('secret-token');
+    expect(() => TbankCrypto.fromBase64('invalid')).toThrow(
+      'Invalid token encryption key',
+    );
+  });
+});