feat: per-event organizer name + reply-to on ticket emails (1.6.1-aio.14)

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

config.json

@@ -1,6 +1,6 @@
 {
   "id": "events",
-  "version": "1.6.1-aio.13",
+  "version": "1.6.1-aio.14",
   "name": "Events",
   "repo": "https://git.atitlan.io/aiolabs/events",
   "short_description": "Sell and register event tickets",