fix(nostr): log publish skips at WARNING instead of silently

Both paths that decline to publish a NIP-52 calendar event were
invisible at the INFO level instances actually run at: the
`signer is None` branch returned bare with no log at any level, and
the missing-client branch logged at debug.

A skipped publish leaves the relay serving whatever inventory it last
saw, so the public ticket count stops tracking the DB with nothing to
indicate it. That has now been found twice, both times only because a
human noticed a wrong number on a public page — #35 on aio-demo, and
on cfaun where an event drifted for 14 days and produced no log line
at all, success or failure.

Both messages name the event id and whether it was a publish or a
delete, so a skip can be tied to a specific event without correlating
timestamps by hand.

Refs #51

nostr_publisher.py

@@ -172,7 +172,14 @@ async def publish_event_to_nostr(
     Returns the published NostrEvent for metadata storage, or None on failure.
     """
     if not nostr_client:
-        logger.debug("[EVENTS] No NostrClient available, skipping publish")
+        # WARNING, not debug: with no client the event is never queued, so
+        # the relay keeps serving stale inventory and nothing downstream
+        # can tell. At debug this skip is invisible at the INFO level
+        # instances actually run at (aiolabs/events#35, #51).
+        logger.warning(
+            "[EVENTS] No NostrClient, skipping NIP-52 "
+            f"{'delete' if delete else 'publish'} for event {event.id}"
+        )
         return None
 
     try: