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)

backend/src/modules/tts/tts.controller.ts

@@ -46,13 +46,27 @@ export class TtsController {
     const ext = file.originalname ? path.extname(file.originalname) || '.aac' : '.aac'
     const dest = path.join(uploadDir, file.filename + ext)
     fs.renameSync(file.path, dest)
+
+    let wavPath = dest
+    if (ext.toLowerCase() !== '.wav') {
+      const potentialWav = dest.replace(/\.[^.]+$/, '.wav')
+      try {
+        execSync(`ffmpeg -y -i "${dest}" -ar 16000 -ac 1 -c:a pcm_s16le "${potentialWav}"`, {
+          timeout: 30000, encoding: 'utf8', stdio: 'pipe',
+        })
+        wavPath = potentialWav
+      } catch (e: any) {
+        this.logger.warn(`FFmpeg conversion failed: ${e.message}, using original format`)
+      }
+    }
+
     try {
       if (process.env.OPENAI_API_KEY) {
         const result = execSync(
           `curl -s -X POST https://api.openai.com/v1/audio/transcriptions \
             -H "Authorization: Bearer ${process.env.OPENAI_API_KEY}" \
             -H "Content-Type: multipart/form-data" \
-            -F "file=@${dest}" \
+            -F "file=@${wavPath}" \
             -F "model=whisper-1" \
             -F "language=zh"`,
           { encoding: 'utf8', timeout: 30000 },
@@ -60,7 +74,7 @@ export class TtsController {
         const parsed = JSON.parse(result)
         if (parsed.text) return { text: parsed.text.trim() }
       }
-      const whisperResult = execSync(`python3 -c 'import sys, whisper; model = whisper.load_model("tiny"); print(model.transcribe(sys.argv[1], language="zh")["text"].strip())' "${dest}"`, { encoding: 'utf8', timeout: 60000 })
+      const whisperResult = execSync(`python3 -c 'import sys, whisper; model = whisper.load_model("tiny"); print(model.transcribe(sys.argv[1], language="zh")["text"].strip())' "${wavPath}"`, { encoding: 'utf8', timeout: 60000 })
       if (whisperResult && whisperResult.trim()) {
         return { text: whisperResult.trim() }
       }
@@ -68,7 +82,8 @@ export class TtsController {
       this.logger.error(`ASR failed: ${e?.message || e}`)
     }
     // 清理临时文件
-    try { fs.unlinkSync(dest) } catch {}
+    try { if (dest) fs.unlinkSync(dest) } catch {}
+    try { if (wavPath && wavPath !== dest) fs.unlinkSync(wavPath) } catch {}
     return { text: '' }
   }
 }