implement registration-confirmation-email

- Add qrbill and pillow dependencies for Swiss QR-bill PNG generation
- Add _STRINGS_DE / _STRINGS_EN bilingual string tables to AdminNotifier
- Add _generate_qr_bill_png(): Swiss QR code with cross overlay (PNG bytes)
- Add _build_parent_html(): HTML confirmation with inline cid:qrbill image
- Add _build_parent_text(): plain-text fallback with IBAN in full
- Add notify_parent(): multipart/mixed MIME email to parent on completion
- Persist metadata.language in _build_record() in json_store.py
- Wire notify_parent() into src/agent/core.py and chat_app.py completion events
- Add 9 tests for notify_parent, _generate_qr_bill_png, language fallback
- Update tasks.md: tasks 1–5 complete; task 6 (smoke test) remains manual

112 tests passing.

https://claude.ai/code/session_01LjjK7RjKVnC8bETtccfgna

tests/test_notifier.py

@@ -1,11 +1,25 @@
 """Tests for AdminNotifier helper methods."""
 
+import email
+from email.header import decode_header
+
 import pytest
 
-from src.notifications.notifier import AdminNotifier
+from src.notifications.notifier import AdminNotifier, _STRINGS_DE, _STRINGS_EN
 from src.models.registration import RegistrationData, Booking, BookingDay
 
 
+def _decoded_subject(msg_str: str) -> str:
+    """Parse a raw MIME message string and return the decoded Subject header."""
+    msg = email.message_from_string(msg_str)
+    raw_subject = msg.get("Subject", "")
+    parts = decode_header(raw_subject)
+    return "".join(
+        chunk.decode(enc or "utf-8") if isinstance(chunk, bytes) else chunk
+        for chunk, enc in parts
+    )
+
+
 @pytest.fixture
 def notifier():
     return AdminNotifier(
@@ -135,3 +149,119 @@ class TestSend:
         recipients = call_args[0][1]  # positional arg: to_addrs
         assert "a@example.com" in recipients
         assert "b@example.com" in recipients
+
+
+# ---------------------------------------------------------------------------
+# notify_parent — parent confirmation email
+# ---------------------------------------------------------------------------
+
+
+@pytest.fixture
+def notifier_no_smtp():
+    """Notifier in dev mode (no SMTP host)."""
+    return AdminNotifier(
+        smtp_host="",
+        smtp_port=587,
+        username="",
+        password="",
+        from_email="agent@example.com",
+    )
+
+
+class TestNotifyParent:
+    def test_notify_parent_calls_send(self, notifier, complete_registration, mocker):
+        """notify_parent dispatches an email to the parent address."""
+        mock_smtp_cls = mocker.patch("smtplib.SMTP")
+        mock_server = mock_smtp_cls.return_value
+
+        notifier.notify_parent(complete_registration, language="de")
+
+        mock_server.sendmail.assert_called_once()
+        call_args = mock_server.sendmail.call_args
+        recipients = call_args[0][1]
+        assert "anna.muster@example.com" in recipients
+
+    def test_notify_parent_german_subject(self, notifier, complete_registration, mocker):
+        """German language produces a German subject line."""
+        mock_smtp_cls = mocker.patch("smtplib.SMTP")
+        captured = {}
+
+        def fake_sendmail(from_, to_, msg_str):
+            captured["msg"] = msg_str
+
+        mock_smtp_cls.return_value.sendmail.side_effect = fake_sendmail
+
+        notifier.notify_parent(complete_registration, language="de")
+
+        assert "Anmeldebestätigung" in _decoded_subject(captured["msg"])
+
+    def test_notify_parent_english_subject(self, notifier, complete_registration, mocker):
+        """English language produces an English subject line."""
+        mock_smtp_cls = mocker.patch("smtplib.SMTP")
+        captured = {}
+
+        def fake_sendmail(from_, to_, msg_str):
+            captured["msg"] = msg_str
+
+        mock_smtp_cls.return_value.sendmail.side_effect = fake_sendmail
+
+        notifier.notify_parent(complete_registration, language="en")
+
+        assert "Registration Confirmation" in _decoded_subject(captured["msg"])
+
+    def test_notify_parent_unknown_language_falls_back_to_de(
+        self, notifier, complete_registration, mocker
+    ):
+        """Unsupported language codes fall back to German."""
+        mock_smtp_cls = mocker.patch("smtplib.SMTP")
+        captured = {}
+
+        def fake_sendmail(from_, to_, msg_str):
+            captured["msg"] = msg_str
+
+        mock_smtp_cls.return_value.sendmail.side_effect = fake_sendmail
+
+        notifier.notify_parent(complete_registration, language="fr")
+
+        assert "Anmeldebestätigung" in _decoded_subject(captured["msg"])
+
+    def test_notify_parent_no_smtp_skips_send(
+        self, notifier_no_smtp, complete_registration, mocker
+    ):
+        """When SMTP host is empty, no sendmail call is made."""
+        mock_smtp_cls = mocker.patch("smtplib.SMTP")
+
+        notifier_no_smtp.notify_parent(complete_registration, language="de")
+
+        mock_smtp_cls.assert_not_called()
+
+    def test_notify_parent_text_body_contains_iban(self, notifier_no_smtp, complete_registration):
+        """Plain-text body includes the IBAN so payment is possible without the QR image."""
+        text = notifier_no_smtp._build_parent_text(complete_registration, _STRINGS_DE)
+        assert "CH14" in text
+
+    def test_notify_parent_text_body_english_contains_iban(
+        self, notifier_no_smtp, complete_registration
+    ):
+        """English plain-text body also includes the IBAN."""
+        text = notifier_no_smtp._build_parent_text(complete_registration, _STRINGS_EN)
+        assert "CH14" in text
+
+
+# ---------------------------------------------------------------------------
+# _generate_qr_bill_png
+# ---------------------------------------------------------------------------
+
+
+class TestGenerateQrBillPng:
+    def test_returns_nonempty_bytes(self, notifier):
+        """_generate_qr_bill_png returns a non-empty bytes object (PNG)."""
+        png = notifier._generate_qr_bill_png()
+        assert isinstance(png, bytes)
+        assert len(png) > 0
+
+    def test_returns_png_signature(self, notifier):
+        """Output starts with the PNG magic bytes."""
+        png = notifier._generate_qr_bill_png()
+        # PNG files start with the 8-byte signature \x89PNG\r\n\x1a\n
+        assert png[:4] == b"\x89PNG"