feat(note): improve audio MIME type detection during upload

- Replaced direct MIME type retrieval with a new method `detectAudioMimeType` to enhance stability in environments without fileinfo support.
- The new method prioritizes file extensions and falls back to the original file name if necessary, ensuring reliable MIME type detection for audio files.

app/note/service/NoteService.php

@@ -249,7 +249,11 @@ class NoteService
         $audio->file_path = $savedPath;
         $audio->file_url = $this->buildPublicFileUrl($savedPath);
         $audio->file_size = (int) $file->getSize();
-        $audio->mime_type = (string) $file->getMime();
+        /**
+         * 线上环境若未启用 fileinfo/finfo，ThinkPHP 的 getMime() 会直接抛错。
+         * 这里改为按文件扩展名做稳定兜底，避免“文件已写入磁盘但接口因取 mime 失败而整体报错”。
+         */
+        $audio->mime_type = $this->detectAudioMimeType($savedPath, $file);
         $audio->duration_ms = max(0, $durationMs);
         $audio->updated_at = $now;
         $audio->save();
@@ -409,6 +413,37 @@ class NoteService
         ];
     }
 
+    /**
+     * 推断音频 MIME。
+     *
+     * 优先使用文件扩展名，避免依赖 fileinfo 扩展；若扩展名缺失，再尝试读取客户端原始文件名。
+     *
+     * @param string $savedPath
+     * @param File $file
+     * @return string
+     */
+    private function detectAudioMimeType(string $savedPath, File $file): string
+    {
+        $extension = strtolower((string) pathinfo($savedPath, PATHINFO_EXTENSION));
+        if ($extension === '') {
+            $extension = strtolower((string) pathinfo((string) $file->getOriginalName(), PATHINFO_EXTENSION));
+        }
+
+        $mimeMap = [
+            'aac' => 'audio/aac',
+            'amr' => 'audio/amr',
+            'm4a' => 'audio/mp4',
+            'mp3' => 'audio/mpeg',
+            'mp4' => 'audio/mp4',
+            'ogg' => 'audio/ogg',
+            'pcm' => 'audio/L16',
+            'wav' => 'audio/wav',
+            'webm' => 'audio/webm',
+        ];
+
+        return $mimeMap[$extension] ?? 'application/octet-stream';
+    }
+
     /**
      * 规范化标题
      *