fix: clean up fight event listeners after completion (BUG-12)

Move fightEvents.cleanup(fightId) to finally block to ensure
cleanup runs even if post-fight operations (bets, payouts) fail.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/engine/orchestrator.ts

@@ -555,6 +555,7 @@ async function executeFightRounds(fightId: string, botA: BotRecord, botB: BotRec
     potSats: mode === 'ranked' ? 42 : 0,
   })
 
+  try {
     // Publish notable results to Nostr
     if (winnerId) {
       const winner = winnerId === botA.id ? botA : botB
@@ -608,8 +609,9 @@ async function executeFightRounds(fightId: string, botA: BotRecord, botB: BotRec
         }
       }
     }
-
+  } finally {
     fightEvents.cleanup(fightId)
+  }
 }
 
 export async function runFight(botAId: string, botBId: string, mode: 'free' | 'ranked' = 'free'): Promise<string> {