feat: practice button on profile, fix rate limiter, fix mobile sprite rendering

- Add Practice button to BotProfilePage for quick sparring
- Fix rate limiter bug: all rateLimit() instances shared one counter map,
  causing global and per-route limits to corrupt each other. Each limiter
  now gets its own isolated map.
- Replace 8-digit hex colors (#ffd70066) with rgba() in sprite rendering
  for mobile browser compatibility (iOS Safari renders them as black boxes)

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

frontend/src/game/sprites/human.ts

@@ -1115,8 +1115,8 @@ export function generateHumanSpriteSheet(
         const r = 40 + Math.sin(t * Math.PI * 4 + a * 0.8) * 8
         const gx = cx + xOff + Math.round(Math.cos(angle) * r)
         const gy = by + Math.floor(bodyH / 2) + Math.round(Math.sin(angle) * r)
-        fill(gx - 1, gy - 1, 3, 3, '#ffcc4430', ox, oy)
-        px(gx, gy, '#ffcc4460', ox, oy)
+        fill(gx - 1, gy - 1, 3, 3, 'rgba(255,204,68,0.19)', ox, oy)
+        px(gx, gy, 'rgba(255,204,68,0.38)', ox, oy)
       }
     }
 
@@ -1141,7 +1141,7 @@ export function generateHumanSpriteSheet(
       }
       fill(hx + 2, hy - 4, 4, 2, hatLt, ox, oy) // highlight
       // Visor
-      fill(hx + 2, hy + 1, headW - 4, 3, '#33333388', ox, oy)
+      fill(hx + 2, hy + 1, headW - 4, 3, 'rgba(51,51,51,0.53)', ox, oy)
     } else if (costume.hatShape === 'pointy') {
       for (let h = 0; h < 18; h++) {
         const w = Math.max(1, Math.floor((headW + 2) * (1 - h / 18)))
@@ -1847,7 +1847,7 @@ export function generateHumanFighterSpriteSheet(
         const r = Math.floor(bodyW / 2) + 6
         const gx = cx + hOff + Math.round(Math.cos(angle) * r)
         const gy = by + Math.floor(bodyH / 2) + Math.round(Math.sin(angle) * r * 0.6)
-        if ((frame + a) % 3 !== 0) px(gx, gy, a % 2 === 0 ? '#ffd700' : '#ffcc4460', ox, oy)
+        if ((frame + a) % 3 !== 0) px(gx, gy, a % 2 === 0 ? '#ffd700' : 'rgba(255,204,68,0.38)', ox, oy)
       }
     }
   }

frontend/src/game/sprites/index.ts

@@ -210,10 +210,10 @@ export function generateSpriteSheet(
       // Tier 4+: full golden ₿ with glow
       if (tier >= 4) {
         // Golden glow behind
-        px(ec - 2, ey, '#ffd70066', ox, oy)
-        px(ec + 2, ey, '#ffd70066', ox, oy)
-        px(ec, ey - 2, '#ffd70066', ox, oy)
-        px(ec, ey + 2, '#ffd70066', ox, oy)
+        px(ec - 2, ey, 'rgba(255,215,0,0.4)', ox, oy)
+        px(ec + 2, ey, 'rgba(255,215,0,0.4)', ox, oy)
+        px(ec, ey - 2, 'rgba(255,215,0,0.4)', ox, oy)
+        px(ec, ey + 2, 'rgba(255,215,0,0.4)', ox, oy)
       }
       const bc = tier >= 4 ? '#ffd700' : tier >= 2 ? '#ff8c00' : '#ff6600'
       // Vertical stroke
@@ -298,8 +298,8 @@ export function generateSpriteSheet(
           px(projX + 1, projY + 1, '#ffaa00', ox, oy)
           px(projX + 2, projY, '#ffcc00', ox, oy)
           px(projX - 1, projY, '#ff2200', ox, oy)
-          px(projX - 2, projY + 1, '#ff440066', ox, oy)
-          px(projX - 3, projY, '#ff220044', ox, oy)
+          px(projX - 2, projY + 1, 'rgba(255,68,0,0.4)', ox, oy)
+          px(projX - 3, projY, 'rgba(255,34,0,0.27)', ox, oy)
         } else {
           px(projX, projY, '#00eeff', ox, oy)
           px(projX + 1, projY - 1, '#44ffff', ox, oy)

frontend/src/pages/BotProfilePage.vue

@@ -7,6 +7,7 @@ import HumanPreview from '../components/HumanPreview.vue'
 import WalletConnect from '../components/WalletConnect.vue'
 import BetHistory from '../components/BetHistory.vue'
 import type { SpriteCustomization } from '../game/sprites'
+import { ensureAudioContext } from '../game/audio'
 
 const route = useRoute()
 const router = useRouter()
@@ -84,6 +85,7 @@ interface QueueEntry {
 const stats = ref<BotStats | null>(null)
 const isLoading = ref(true)
 const isJoining = ref(false)
+const isJoiningPractice = ref(false)
 const showChoose = ref(false)
 const waitingFighters = ref<QueueEntry[]>([])
 let pollHandle: ReturnType<typeof setInterval> | null = null
@@ -345,6 +347,31 @@ async function fightSpecific(opponentBotId: string) {
   isJoining.value = false
 }
 
+async function practice() {
+  if (!stats.value || isJoiningPractice.value) return
+  isJoiningPractice.value = true
+  fightError.value = ''
+  ensureAudioContext()
+  try {
+    const res = await fetch(`/api/fights/practice/${stats.value.id}`, { method: 'POST' })
+    if (res.ok) {
+      const data = await res.json()
+      router.push(`/arena/${data.fightId}`)
+      return
+    } else {
+      const data = await res.json()
+      if (data.fightId) {
+        fightError.value = 'Already in a fight!'
+      } else {
+        fightError.value = data.retryAfterSec ? `${data.error} (${data.retryAfterSec}s)` : (data.error || 'Practice failed.')
+      }
+    }
+  } catch {
+    fightError.value = 'Network error.'
+  }
+  isJoiningPractice.value = false
+}
+
 function handleSignOut() {
   logout()
   router.push('/')
@@ -548,6 +575,20 @@ const tierClass = (t: number) => `tier-${t}`
               </button>
             </div>
 
+            <!-- Practice -->
+            <button
+              class="w-full mt-2 py-2.5 bg-white/3 border border-white/10 text-text-muted
+                     font-display font-bold text-xs tracking-widest
+                     hover:bg-white/5 hover:text-text-secondary transition-all
+                     disabled:opacity-50 disabled:cursor-wait
+                     flex items-center justify-center gap-2"
+              :disabled="isJoiningPractice"
+              @click="practice"
+            >
+              <span v-if="isJoiningPractice" class="w-3.5 h-3.5 border-2 border-white/20 border-t-white/50 rounded-full animate-spin" />
+              {{ isJoiningPractice ? 'STARTING...' : 'PRACTICE' }}
+            </button>
+
             <p v-if="fightError" class="font-mono text-[10px] text-neon-pink mt-2">{{ fightError }}</p>
 
             <!-- Choose your fight panel -->