feat: "Email sent" column and per-event copy-to-organizer BCC

Organizers had no way to see whether a ticket email went out short of
reading the Postfix journal, and no copy of what the attendee received —
LNbits submits over SMTP, so nothing lands in a Sent folder.

- Admin ticket table gains an "Email sent" column derived from
  `extra.email_notification_sent` ("✓ sent" / "not sent" / "unpaid" /
  "no email").
- `extra.copy_to_organizer`: BCC every ticket email to the event's
  reply-to address (explicit, else the owner's account email) on the SMTP
  envelope only — no Bcc/To header, and skipped when the buyer *is* that
  address. Toggle sits with the other delivery switches in the admin form.

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

static/js/index.vue

@@ -804,6 +804,14 @@
               label="Nostr notifications"
               left-label
             ></q-toggle>
+            <q-toggle
+              v-model="formDialog.data.extra.copy_to_organizer"
+              label="Send me a copy of each ticket email"
+              left-label
+            ></q-toggle>
+            <div class="text-caption text-grey-7">
+              Copies go to the reply-to address (or your account email).
+            </div>
           </q-expansion-item>
 
           <q-separator class="q-my-md"></q-separator>