feat: record stream interruption reasons via StreamStatus

- Add StreamStatus type (relay/common) to track stream end reason
  (done/timeout/client_gone/scanner_error/eof/panic/ping_fail) and
  accumulate soft errors during streaming via sync.Once + sync.Mutex.
- Add StreamResult (relay/helper) as the callback interface: adapters
  call sr.Error() for soft errors, sr.Stop() for fatal, sr.Done() for
  normal completion. No early-return problem — multiple errors per chunk
  are naturally supported.
- Refactor StreamScannerHandler callback from func(string) bool to
  func(string, *StreamResult). All 9 channel adapters updated.
- Write stream_status into log other JSON field (admin-only) with
  status ok/error, end_reason, error_count, and error messages.
- Frontend: display stream status in log detail expansion for admins.

relay/channel/openai/audio.go

@@ -35,21 +35,21 @@ func OpenaiTTSHandler(c *gin.Context, resp *http.Response, info *relaycommon.Rel
 	c.Writer.WriteHeader(resp.StatusCode)
 
 	if info.IsStream {
-		helper.StreamScannerHandler(c, resp, info, func(data string) bool {
+		helper.StreamScannerHandler(c, resp, info, func(data string, sr *helper.StreamResult) {
 			if service.SundaySearch(data, "usage") {
 				var simpleResponse dto.SimpleResponse
-				err := common.Unmarshal([]byte(data), &simpleResponse)
-				if err != nil {
+				if err := common.Unmarshal([]byte(data), &simpleResponse); err != nil {
 					logger.LogError(c, err.Error())
-				}
-				if simpleResponse.Usage.TotalTokens != 0 {
+					sr.Error(err)
+				} else if simpleResponse.Usage.TotalTokens != 0 {
 					usage.PromptTokens = simpleResponse.Usage.InputTokens
 					usage.CompletionTokens = simpleResponse.OutputTokens
 					usage.TotalTokens = simpleResponse.TotalTokens
 				}
 			}
-			_ = helper.StringData(c, data)
-			return true
+			if err := helper.StringData(c, data); err != nil {
+				sr.Error(err)
+			}
 		})
 	} else {
 		common.SetContextKey(c, constant.ContextKeyLocalCountTokens, true)