fix: use coincurve instead of secp256k1 for Nostr event signing

- Replace secp256k1.PrivateKey with coincurve.PrivateKey to match
  the sign_event function signature in lnbits/utils/nostr.py
- Remove internal try/except so exceptions propagate to caller,
  fixing misleading success logs when publishing actually fails

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lnbits/core/services/users.py

@@ -268,12 +268,9 @@ async def _create_default_pay_link(account: Account, wallet) -> None:
 
 async def _publish_nostr_metadata_event(account: Account) -> None:
     """Publish a Nostr kind 0 metadata event for a new user"""
-    try:
-        import importlib
-        import sys
-        import secp256k1
+    import coincurve
 
-        # Note: We publish directly to nostrrelay database, no need to get relay URLs
+    from lnbits.utils.nostr import sign_event
 
     # Create Nostr kind 0 metadata event
     metadata = {
@@ -289,11 +286,8 @@ async def _publish_nostr_metadata_event(account: Account) -> None:
         "content": json.dumps(metadata),
     }
 
-        # Sign the event using LNbits utilities
-        from lnbits.utils.nostr import sign_event
-
-        # Convert hex private key to secp256k1 PrivateKey
-        private_key = secp256k1.PrivateKey(bytes.fromhex(account.prvkey))
+    # Convert hex private key to coincurve PrivateKey
+    private_key = coincurve.PrivateKey(bytes.fromhex(account.prvkey))
 
     # Sign the event
     signed_event = sign_event(event, account.pubkey, private_key)
@@ -301,10 +295,6 @@ async def _publish_nostr_metadata_event(account: Account) -> None:
     # Publish directly to nostrrelay database (hacky but works around WebSocket issues)
     await _insert_event_into_nostrrelay(signed_event, account.username)
 
-    except Exception as e:
-        logger.error(f"Failed to publish Nostr metadata event: {e}")
-        # Don't raise - we don't want user creation to fail if Nostr publishing fails
-
 
 async def _insert_event_into_nostrrelay(event: dict, username: str) -> None:
     """Directly insert Nostr event into nostrrelay database (hacky workaround)"""