feat(billing): 火山方舟视频计费 - 支持真实 Token 预授权与结算

Refs #228

Co-authored-by: MasterChiefCN <49179444+MasterChiefCN@users.noreply.github.com>

backend/internal/service/analytics.go

@@ -940,6 +940,14 @@ func (s *Service) EnrichAPICallLog(log *model.ApiCallLog, responseBody []byte) {
 		log.UsageAvailable = true
 		log.InputTokens = firstInt64(usage, "input_tokens", "prompt_tokens")
 		log.OutputTokens = firstInt64(usage, "output_tokens", "completion_tokens")
+		// 火山方舟视频的输入 Token 恒为 0；查询任务以 completion_tokens 为实际用量，
+		// 兼容只返回 total_tokens 的同协议中转实现。
+		if log.Capability == "video" && strings.Contains(log.Path, "/contents/generations/tasks") && log.OutputTokens == 0 {
+			log.OutputTokens = firstInt64(usage, "total_tokens")
+		}
+		if log.Capability == "video" && strings.Contains(log.Path, "/contents/generations/tasks") && log.OutputTokens <= 0 {
+			log.UsageAvailable = false
+		}
 		if details, ok := usage["input_tokens_details"].(map[string]any); ok {
 			log.CachedTokens = firstInt64(details, "cached_tokens")
 		}