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/BotProfilePage.vue

@@ -409,10 +409,11 @@ const tierClass = (t: number) => `tier-${t}`
                 class="flex-1 py-3 bg-neon-pink/10 border-2 border-neon-pink/50 text-neon-pink
                        font-display font-black text-sm tracking-wider
                        hover:bg-neon-pink/20 transition-all neon-border-pink
-                       disabled:opacity-30 disabled:cursor-not-allowed"
+                       disabled:opacity-50 disabled:cursor-wait flex items-center justify-center gap-2"
                 :disabled="isJoining"
                 @click="instantFight"
               >
+                <span v-if="isJoining" class="w-4 h-4 border-2 border-neon-pink/30 border-t-neon-pink rounded-full animate-spin" />
                 {{ isJoining ? 'MATCHING...' : 'INSTANT FIGHT' }}
               </button>
               <button