fix: AudioContext 复用 + 盲盒加载错误提示 + icon 按钮 aria-label

- #27: panic/blindbox/ShareCardModal/AuthModal 中 icon-only 按钮补 aria-label
- #28: playChime 缓存复用单个 AudioContext，避免超出浏览器 ~6 个上限
- #29: 已完成（上一批次 ApiError.name = "ApiError"）
- #30: blindbox lobby fetchRooms 失败时显示"加载失败/点击重试"
- #31: 已完成（theme.ts VALID_THEMES 校验）

src/lib/celebrate.ts

@@ -62,9 +62,20 @@ export function fireCelebration() {
   setTimeout(frame, 300);
 }
 
+let _audioCtx: AudioContext | null = null;
+
+function getAudioContext(): AudioContext {
+  if (!_audioCtx || _audioCtx.state === "closed") {
+    _audioCtx = new AudioContext();
+  }
+  return _audioCtx;
+}
+
 export function playChime() {
   try {
-    const ctx = new AudioContext();
+    const ctx = getAudioContext();
+    if (ctx.state === "suspended") ctx.resume();
+
     const gain = ctx.createGain();
     gain.connect(ctx.destination);
     gain.gain.setValueAtTime(0.15, ctx.currentTime);
@@ -88,8 +99,6 @@ export function playChime() {
       osc.start(start);
       osc.stop(start + 0.6);
     });
-
-    setTimeout(() => ctx.close(), 2000);
   } catch {
     // Audio not available — silent fallback
   }