chore: rebase onto upstream v1.6.1 + bump to v1.6.1-aio.1

Rebases the aio fork onto upstream v1.6.1 (4bf867e), pulling in:
- fiat checkout + email/Nostr DM ticket notifications (PR #50)
- currency-conversion fix (v1.5.0)
- custom notification subject/body (v1.6.0)
- resend-email button on the ticket list (PR #51)

Notable merges:
- views_api.api_event_update keeps the explicit-field-list gating from
  the aio.4 security fix, with allow_fiat + fiat_currency added so an
  owner editing a fiat-enabled event keeps the fiat config.
- models.PublicEvent now exposes both upstream's fiat fields and our
  location / categories / status fields.
- migrations.py reverts to byte-identical to upstream v1.6.1 (no aio
  entries); fork schema lives in migrations_fork.py (per aiolabs/lnbits#8).
- Lint reformatted with black + ruff to match upstream style.

Contributors entry adds `padreug` (aio fork maintainer).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

nostr_sync.py

@@ -137,9 +137,11 @@ async def wait_for_nostr_events(nostr_client: NostrClient):
     while True:
         try:
             # Subscribe to NIP-52 calendar events
-            await nostr_client.subscribe([
-                {"kinds": [31922, 31923]},
-            ])
+            await nostr_client.subscribe(
+                [
+                    {"kinds": [31922, 31923]},
+                ]
+            )
 
             # Process incoming events
             while True: