refactor: extract shared FightData interface to fight/types.ts

Move FightData, FightRound, FightBot, FightArenaInfo types from local
definitions in FightViewer.vue to shared fight/types.ts. Replace `any`
typing in HumanFightPage, FightPage, useFightPolling, and useFightCache
with proper typed interfaces. Fix null-safety guards exposed by typing.

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

frontend/src/composables/useFightPolling.ts

@@ -1,4 +1,5 @@
 import { ref, type Ref } from 'vue'
+import type { FightData, FightBot, FightArenaInfo } from '../game/fight/types'
 
 export interface LiveLogItem {
   type: string
@@ -8,11 +9,12 @@ export interface LiveLogItem {
 }
 
 export interface LiveFightData {
-  botA: any
-  botB: any
+  botA: FightBot | null
+  botB: FightBot | null
   arena: string
-  arenaInfo?: { name: string }
-  [key: string]: any
+  arenaInfo?: FightArenaInfo | null
+  mode?: string
+  potSats?: number
 }
 
 interface SSEListenerEntry {
@@ -25,7 +27,7 @@ export function useFightPolling(fightId: Ref<string>) {
   const isLoading = ref(true)
   const liveRounds = ref(0)
   const fightError = ref('')
-  const fight = ref<any>(null)
+  const fight = ref<FightData | null>(null)
   const liveFightData = ref<LiveFightData | null>(null)
   const spectatorCount = ref(0)
   const currentChallengeInfo = ref<{ type: string; label: string } | null>(null)