fix: ASR audio format conversion + share.vue deduplicate share creation

- TTS /tts/asr: convert non-WAV (AAC/MP3) to WAV before whisper transcription
- share.vue: only create share record if no cached shareCode exists
  (prevents duplicate share records on every page load)

zhiyin-app/src/pages/share/share.vue

@@ -178,20 +178,22 @@ async function loadData() {
   if (!token) { uni.showToast({ title: '请先登录', icon: 'none' }); return }
   const header = { Authorization: `Bearer ${token}` }
 
-  // 先创建分享链接，缓存下来供复制使用
-  try {
-    const res = await uni.request({
-      url: api('/share/create'), method: 'POST',
-      data: { type: 'app', title: '我在AI磁场·职引练习面试', description: 'AI模拟面试+简历优化，快来一起提升吧' },
-      header,
-    })
-    if (res.statusCode >= 200 && res.statusCode < 300) {
-      const data = res.data?.data || res.data
-      if (data.shareCode) {
-        shareUrlCached.value = `https://zhiyinwx.yzrcloud.cn/api/share/${data.shareCode}`
+  // 仅在无缓存分享链接时创建新分享记录
+  if (!shareUrlCached.value) {
+    try {
+      const res = await uni.request({
+        url: api('/share/create'), method: 'POST',
+        data: { type: 'app', title: '我在AI磁场·职引练习面试', description: 'AI模拟面试+简历优化，快来一起提升吧' },
+        header,
+      })
+      if (res.statusCode >= 200 && res.statusCode < 300) {
+        const data = res.data?.data || res.data
+        if (data.shareCode) {
+          shareUrlCached.value = `https://zhiyinwx.yzrcloud.cn/api/share/${data.shareCode}`
+        }
       }
-    }
-  } catch (e) { /* create share is best-effort */ }
+    } catch (e) { /* create share is best-effort */ }
+  }
 
   try {
     const [statsRes, recordsRes, visitorsRes] = await Promise.all([