feat: per-event organizer name + reply-to on ticket emails

Each organizer is different, so the sender identity of ticket emails is
now per event rather than per instance:

- `extra.organizer_name` → From display name "Organizer via <site title>"
  (site title alone when unset). The From address stays the instance
  mailbox — that is what DKIM signs — so this costs nothing in mail auth.
- `extra.reply_to_email` → Reply-To; blank falls back to the email on the
  LNbits account that owns the event wallet; no header when neither
  exists. When a reply-to exists the body says "Questions? Reply to this
  email and it reaches <organizer>", and "Organizer: <name>" is listed
  with the ticket details.

Both fields sit next to the existing per-event subject/body in the admin
dialog. The organizer's own wording (in whatever language) remains
`notification_body`.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EYwoAkZZmXMMmaBp4WGUBo

tests/test_ticket_email.py

@@ -87,3 +87,59 @@ def test_payload_includes_event_details_and_qr(monkeypatch):
     assert "/events/api/v1/ticket-card/tkt1" in text
     assert "<img" not in html and "Ticket ID: tkt1" in html
     assert '<a href="https://lnbits.example/events/api/v1/ticket-card/tkt1">' in html
+
+
+def test_reply_to_and_organizer_sender_name(monkeypatch):
+    from ..services import organizer_sender_name
+
+    monkeypatch.setattr(settings, "lnbits_site_title", "Oyez!")
+    event = _event(
+        extra={
+            "organizer_name": "Château du Faune",
+            "reply_to_email": "hello@faune.example",
+        }
+    )
+    assert organizer_sender_name(event) == "Château du Faune via Oyez!"
+    assert organizer_sender_name(_event()) == "Oyez!"
+
+    msg = build_ticket_email(
+        "tickets@example.org",
+        ["ada@example.com"],
+        "Subj",
+        "text",
+        None,
+        reply_to="hello@faune.example",
+        sender_name=organizer_sender_name(event),
+    )
+    assert msg["Reply-To"] == "hello@faune.example"
+    # Non-ASCII display names are RFC 2047-encoded on the wire; decode to compare.
+    from email.header import decode_header, make_header
+
+    assert str(make_header(decode_header(msg["From"]))) == (
+        "Château du Faune via Oyez! <tickets@example.org>"
+    )
+
+    no_reply = build_ticket_email(
+        "tickets@example.org", ["ada@example.com"], "Subj", "text"
+    )
+    assert no_reply["Reply-To"] is None
+
+
+def test_reply_hint_only_when_reply_to_exists(monkeypatch):
+    monkeypatch.setattr(settings, "lnbits_baseurl", "https://lnbits.example/")
+    event = _event(extra={"organizer_name": "Château du Faune"})
+    _, text, _ = _ticket_notification_payload(
+        _ticket(), event, reply_to="hello@faune.example"
+    )
+    assert "Organizer: Château du Faune" in text
+    assert "Reply to this email and it reaches Château du Faune" in text
+    _, text, _ = _ticket_notification_payload(_ticket(), event, reply_to=None)
+    assert "Reply to this email" not in text
+
+
+def test_blank_reply_to_email_is_none():
+    from ..models import EventExtra
+
+    assert EventExtra(reply_to_email="").reply_to_email is None
+    assert EventExtra(reply_to_email="  ").reply_to_email is None
+    assert EventExtra(reply_to_email="a@b.example").reply_to_email == "a@b.example"