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/components/FightViewer.vue

@@ -14,34 +14,7 @@ import {
 } from '../game/audio'
 import { isKokoroLoading, getKokoroProgress } from '../game/tts'
 import { isPerfMode, setPerfMode } from '../game/fight/config'
-
-interface Round {
-  roundNumber: number
-  challengeType: string
-  challengeData: string
-  botAResponse: string | null
-  botATimeMs: number | null
-  botAScore: number | null
-  botBResponse: string | null
-  botBTimeMs: number | null
-  botBScore: number | null
-  winnerId: string | null
-  narration: string | null
-}
-
-interface FightData {
-  id: string
-  botA: { id: string; name: string; avatarSeed: string; archetype?: string; customization?: Record<string, unknown> | null; profilePicUrl?: string | null; eloRating: number; wins: number; losses: number; tier: number; botType?: string } | null
-  botB: { id: string; name: string; avatarSeed: string; archetype?: string; customization?: Record<string, unknown> | null; profilePicUrl?: string | null; eloRating: number; wins: number; losses: number; tier: number; botType?: string } | null
-  arenaInfo: { id: string; name: string; description: string; modifier: string | null } | null
-  arena: string
-  winnerId: string | null
-  botAHp: number
-  botBHp: number
-  totalRounds: number
-  status: string
-  rounds: Round[]
-}
+import type { FightData, FightRound } from '../game/fight/types'
 
 const props = defineProps<{ fight: FightData; autoplay?: boolean }>()
 const emit = defineEmits<{ 'replay-done': [] }>()
@@ -297,7 +270,7 @@ async function showHitText(text: string, color: string, x: number) {
   hitTextVisible.value = false
 }
 
-function addRoundToLog(round: Round, stagger: boolean): Promise<void> {
+function addRoundToLog(round: FightRound, stagger: boolean): Promise<void> {
   if (!stagger) {
     const challenge = JSON.parse(round.challengeData)
     logItems.value.push(