fix: watch another fight route watcher, profile fight button spinner

- Add route param watcher so navigating to a new fight properly resets
  and reinitializes the scene (fixes KAPLAY re-init / null scene errors)
- Add loading spinner to profile page instant fight button
- Restore truncated challenges.ts (was causing all 500 errors)

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

frontend/src/pages/FightPage.vue

@@ -27,6 +27,56 @@ const autoBattleCount = ref(0)
 let pollHandle: ReturnType<typeof setInterval> | null = null
 let pollCount = 0
 
+// Watch route param changes (e.g. "watch another fight" navigating to a new fight)
+watch(() => route.params.fightId, async (newId) => {
+  if (!newId || newId === fightId.value) return
+  // Clean up current state
+  if (pollHandle) { clearInterval(pollHandle); pollHandle = null }
+  stopHumanPolling()
+  disconnectSSE()
+  stopAllAudio()
+  if (liveScene) { liveScene.destroy(); liveScene = null }
+  liveSceneReady.value = false
+
+  // Reset all state
+  fightId.value = newId as string
+  fight.value = null
+  isLoading.value = true
+  isLive.value = false
+  liveRounds.value = 0
+  fightError.value = ''
+  replayDone.value = false
+  autoBattle.value = false
+  autoBattleCount.value = 0
+  liveFightData.value = null
+  liveLogItems.value = []
+  liveHpA.value = 100
+  liveHpB.value = 100
+  liveCurrentRound.value = 0
+  humanChallenge.value = null
+  humanSubmitted.value = false
+  humanFightDone.value = false
+  humanFightResult.value = null
+  pendingChallengeData.value = null
+
+  // Re-load
+  const status = await loadFight()
+  isLoading.value = false
+  if (status === null || status !== 'finished') {
+    isLive.value = true
+  }
+  if (isLive.value) {
+    startPolling()
+    if (isHumanFight.value) {
+      startHumanPolling()
+      connectSSE()
+      await nextTick()
+      await nextTick()
+      if (liveFightData.value) await initLiveScene()
+    }
+  }
+})
+
 // Human fight detection
 const isHumanFight = computed(() => !!myBot.value?.isHuman || myBot.value?.archetype === 'human')