feat(cache): enhance disk cache management with concurrency control and cleanup optimizations

common/disk_cache.go

@@ -127,7 +127,11 @@ func CleanupOldDiskCacheFiles(maxAge time.Duration) error {
 			continue
 		}
 		if now.Sub(info.ModTime()) > maxAge {
-			os.Remove(filepath.Join(dir, entry.Name()))
+			// 注意：后台清理任务删除文件时，由于无法得知原始 base64Size，
+			// 只能按磁盘文件大小扣减。这在目前 base64 存储模式下是准确的。
+			if err := os.Remove(filepath.Join(dir, entry.Name())); err == nil {
+				DecrementDiskFiles(info.Size())
+			}
 		}
 	}
 	return nil

common/disk_cache_config.go

@@ -113,8 +113,12 @@ func IncrementDiskFiles(size int64) {
 
 // DecrementDiskFiles 减少磁盘文件计数
 func DecrementDiskFiles(size int64) {
-	atomic.AddInt64(&diskCacheStats.ActiveDiskFiles, -1)
-	atomic.AddInt64(&diskCacheStats.CurrentDiskUsageBytes, -size)
+	if atomic.AddInt64(&diskCacheStats.ActiveDiskFiles, -1) < 0 {
+		atomic.StoreInt64(&diskCacheStats.ActiveDiskFiles, 0)
+	}
+	if atomic.AddInt64(&diskCacheStats.CurrentDiskUsageBytes, -size) < 0 {
+		atomic.StoreInt64(&diskCacheStats.CurrentDiskUsageBytes, 0)
+	}
 }
 
 // IncrementMemoryBuffers 增加内存缓存计数