feat: attach a self-describing ticket card to the email (1.6.1-aio.10)

The v1.6.1-aio.9 mail still scored 8.4/10 on mail-tester: the remaining
deduction was HTML_IMAGE_ONLY (1.8) — an HTML part whose only content of
note is a remote <img>. Remote images are also blocked by default in most
clients until the reader opts in, and a bare QR saved from that mail says
nothing about what it opens.

- New `qr.py` module (QR + logo helpers moved out of views_api) with
  `render_ticket_card`: site title, event name, when/where, the branded
  QR, name on ticket, ticket id and the door instruction, laid out with
  the bundled DejaVu Sans; `format_event_when` gives "Fri 19 Feb 2027,
  16:00 - 20:00"; filenames are `ticket-<event-slug>-<id8>.png`.
- `GET /events/api/v1/ticket-card/{ticket_id}` serves the same PNG
  (anonymous, like the QR endpoint); the email's "Ticket image" link
  now points there.
- The ticket email becomes multipart/mixed: text + HTML alternatives
  (URLs as links, no <img>) plus the card as a PNG attachment, which
  clients show inline at the end of the message and which works offline
  at the door.

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

services.py

@@ -1,8 +1,10 @@
 from __future__ import annotations
 
 import asyncio
+import re
 import smtplib
 from asyncio.tasks import create_task
+from email.mime.image import MIMEImage
 from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
 from email.utils import formataddr, formatdate, make_msgid
@@ -26,6 +28,13 @@ from .crud import (
 )
 from .models import Event, NotificationDeliveryResult, Ticket, TicketResendResult
 from .nostr_hooks import publish_or_delete_nostr_event
+from .qr import (
+    format_event_when,
+    image_png_bytes,
+    load_qr_logo,
+    render_ticket_card,
+    ticket_card_filename,
+)
 
 DEFAULT_NOSTR_RELAYS = [
     "wss://relay.damus.io",
@@ -118,17 +127,15 @@ def _ticket_notification_message(ticket: Ticket, event: Event) -> tuple[str, str
 def _ticket_details(ticket: Ticket, event: Event) -> str:
     """Human-readable ticket facts for the email body. Also what keeps the
     mail from being an image with no words (SpamAssassin HTML_IMAGE_ONLY)."""
-    when = event.event_start_date
-    if event.event_end_date and event.event_end_date != event.event_start_date:
-        when = f"{when} to {event.event_end_date}"
-    lines = [f"Event: {event.name}", f"When: {when}"]
+    lines = [f"Event: {event.name}", f"When: {format_event_when(event)}"]
     if event.location:
         lines.append(f"Where: {event.location}")
     if ticket.name:
         lines.append(f"Name on ticket: {ticket.name}")
     lines.append(f"Ticket ID: {ticket.id}")
     lines.append(
-        "Show the QR code below (or open the link above on your phone) at the "
+        "Your ticket (with its QR code) is attached to this email — save it "
+        "or open the link above on your phone, and show the QR code at the "
         "door to be scanned in."
     )
     return "\n".join(lines)
@@ -142,14 +149,18 @@ def _ticket_delivery_message(ticket: Ticket, event: Event, base_message: str) ->
 
 
 def _ticket_email_html_message(ticket: Ticket, event: Event, base_message: str) -> str:
+    """HTML twin of the text part. Deliberately no <img>: the card travels
+    as an attachment (renders inline in most clients, works offline, and
+    keeps SpamAssassin's HTML_IMAGE_ONLY rules quiet), and URLs become
+    links."""
     text_message = _ticket_delivery_message(ticket, event, base_message)
-    html_message = f"<p>{escape(text_message).replace(chr(10), '<br />')}</p>"
-    image_url = escape(_ticket_image_url(ticket), quote=True)
-    return (
-        f"{html_message}"
-        f'<p><img src="{image_url}" alt="Ticket QR code" '
-        'style="max-width: 300px; height: auto;" /></p>'
+    html = escape(text_message)
+    html = re.sub(
+        r"(https?://[^\s<]+)",
+        lambda m: f'<a href="{m.group(1)}">{m.group(1)}</a>',
+        html,
     )
+    return f"<p>{html.replace(chr(10), '<br />')}</p>"
 
 
 def _ticket_notification_payload(ticket: Ticket, event: Event) -> tuple[str, str, str]:
@@ -195,8 +206,20 @@ async def _deliver_ticket_notifications(
     if result.email.attempted:
         try:
             assert ticket.email
+            card = render_ticket_card(
+                ticket,
+                event,
+                logo=await load_qr_logo(),
+                site_title=settings.lnbits_site_title,
+            )
             await _send_ticket_email_notification(
-                [ticket.email], text_message, subject, html_message
+                [ticket.email],
+                text_message,
+                subject,
+                html_message,
+                attachments=[
+                    (ticket_card_filename(ticket, event), image_png_bytes(card))
+                ],
             )
             ticket.extra.email_notification_sent = True
             result.email.sent = True
@@ -227,6 +250,7 @@ async def _send_ticket_email_notification(
     message: str,
     subject: str,
     html_message: str | None = None,
+    attachments: list[tuple[str, bytes]] | None = None,
 ) -> None:
     """Multipart (text + HTML) ticket email through the instance SMTP
     settings. Core's `send_email_notification` is plain-text only, which is
@@ -244,7 +268,9 @@ async def _send_ticket_email_notification(
         if not is_valid_email_address(address):
             raise ValueError(f"Invalid email address: {address}")
 
-    msg = build_ticket_email(from_email, to_emails, subject, message, html_message)
+    msg = build_ticket_email(
+        from_email, to_emails, subject, message, html_message, attachments
+    )
     username = settings.lnbits_email_notifications_username or from_email
     await asyncio.to_thread(
         _smtp_send,
@@ -264,22 +290,34 @@ def build_ticket_email(
     subject: str,
     message: str,
     html_message: str | None = None,
+    attachments: list[tuple[str, bytes]] | None = None,
 ) -> MIMEMultipart:
-    """Assemble the multipart ticket email with the headers receivers score
-    on: a Date and a Message-ID (their absence is what SpamAssassin's
-    MISSING_DATE / MISSING_MID flag, and what Gmail/Outlook read as
-    machine-generated), and a display name on From so the sender is not a
-    bare address."""
-    msg = MIMEMultipart("alternative")
+    """Assemble the ticket email: text + HTML alternatives, PNG attachments
+    (the ticket card), and the headers receivers score on — a Date and a
+    Message-ID (their absence is what SpamAssassin's MISSING_DATE /
+    MISSING_MID flag, and what Gmail/Outlook read as machine-generated) and
+    a display name on From so the sender is not a bare address."""
+    body = MIMEMultipart("alternative")
+    body.attach(MIMEText(message, "plain"))
+    if html_message:
+        body.attach(MIMEText(html_message, "html"))
+
+    if attachments:
+        msg = MIMEMultipart("mixed")
+        msg.attach(body)
+        for filename, data in attachments:
+            part = MIMEImage(data, _subtype="png")
+            part.add_header("Content-Disposition", "attachment", filename=filename)
+            msg.attach(part)
+    else:
+        msg = body
+
     sender_name = (settings.lnbits_site_title or "").strip() or "Tickets"
     msg["From"] = formataddr((sender_name, from_email))
     msg["To"] = ", ".join(to_emails)
     msg["Subject"] = subject
     msg["Date"] = formatdate(localtime=True)
     msg["Message-ID"] = make_msgid(domain=from_email.rsplit("@", 1)[-1])
-    msg.attach(MIMEText(message, "plain"))
-    if html_message:
-        msg.attach(MIMEText(html_message, "html"))
     return msg
 
 
@@ -318,11 +356,13 @@ def _ticket_url(ticket: Ticket) -> str:
 
 
 def _ticket_image_url(ticket: Ticket) -> str:
-    """The QR PNG is served by THIS extension on the LNbits host, so it is
-    built from `lnbits_baseurl` even when `ticket_base_url` points at a
-    separate web app (deviation from upstream, which assumes both are the
+    """The ticket card PNG is served by THIS extension on the LNbits host, so
+    it is built from `lnbits_baseurl` even when `ticket_base_url` points at
+    a separate web app (deviation from upstream, which assumes both are the
     same host)."""
-    return f"{settings.lnbits_baseurl.rstrip('/')}/events/api/v1/qr/{ticket.id}"
+    return (
+        f"{settings.lnbits_baseurl.rstrip('/')}/events/api/v1/ticket-card/{ticket.id}"
+    )
 
 
 async def refund_tickets(event_id: str):