docs: guest checkout contract, upstream-candidates log; bump 1.6.1-aio.8

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

README.md

@@ -23,7 +23,6 @@ Events includes a shareable ticket scanner, which can be used to register attend
 1. Create an event\
    ![create event](https://i.imgur.com/dadK1dp.jpg)
 2. Fill out the event information:
-
    - event name
    - wallet (normally there's only one)
    - event information
@@ -34,7 +33,6 @@ Events includes a shareable ticket scanner, which can be used to register attend
 
 3. Share the event registration link\
    ![event ticket](https://imgur.com/AQWUOBY.jpg)
-
    - ticket example\
      ![ticket example](https://i.imgur.com/trAVSLd.jpg)
 
@@ -44,6 +42,31 @@ Events includes a shareable ticket scanner, which can be used to register attend
 4. Use the built-in ticket scanner to validate registered, and paid, attendees\
    ![ticket scanner](https://i.imgur.com/zrm9202.jpg)
 
+## Guest checkout, card payments and email delivery (aio fork)
+
+- **Identity.** `POST /events/api/v1/tickets/{event_id}` accepts either an
+  LNbits `user_id` or a guest `name` + `email`; a `user_id` ticket may also
+  carry an `email` so logged-in buyers get their ticket mailed.
+- **Payment methods.** `extra.payment_methods` (`lightning`, `fiat`) lists the
+  rails an event accepts; an empty list keeps the legacy rule (Lightning always,
+  fiat when `allow_fiat`). The effective list is published on the NIP-52 event
+  as `tickets_payment_methods` and enforced at purchase.
+- **Return to the calling app.** A client may send `frontend_url` (its app
+  root, e.g. `https://app.example/events`). Its origin must be one of
+  `LNBITS_CORS_ALLOWED_ORIGINS`, the LNbits base URL or
+  `LNBITS_CUSTOM_FRONTEND_URL`, otherwise the request is refused. Under that
+  root the extension builds the Stripe `success_url`
+  (`/events/{event_id}?checkout=success&tickets=<id,id>`), `cancel_url`
+  (`/events/{event_id}?checkout=cancelled`) and the emailed ticket link
+  (`/events/ticket/{ticket_id}`). Absent, the LNbits host is used as before.
+- **Stripe session.** The buyer's email is passed as `customer_email`
+  (prefilled and locked on the hosted page); the line item is named after the
+  event; `event_id`, `quantity` and `ticket_ids` ride along as metadata.
+- **Email.** Multipart text + HTML with the ticket QR embedded from
+  `GET /events/api/v1/qr/{ticket_id}` (PNG, branded with the instance QR logo).
+  `POST /events/api/v1/tickets/{ticket_id}/resend-email` returns a
+  `TicketResendResult` with per-channel outcome.
+
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