fix(provider): 延长媒体超时并终止超时轮转

将图像和视频的默认 HTTP/轮询超时分别提高到 20 分钟和 30 分钟。媒体任务超时后直接失败，不再重试、切换客户端或标记为 upstream_submission_unknown。OpenAI 图像端点遇到上游明确拒绝 response_format 时自动移除并缓存兼容结论。

验证：go test ./... -count=1；go vet ./...；gofmt；相关 Shell bash -n、ShellCheck 与发布脚本回归测试。

apps/api/internal/clients/topaz.go

@@ -163,7 +163,7 @@ func (c TopazClient) prepareSource(ctx context.Context, request Request, rawURL
 	downloadClient := topazSourceHTTPClient(httpClient(request.HTTPClient, c.HTTPClient), boolishDefault(request.Candidate.PlatformConfig["allowPrivateSourceDownloads"], false))
 	resp, err := downloadClient.Do(req)
 	if err != nil {
-		return topazSource{}, &ClientError{Code: "network", Message: err.Error(), Retryable: true}
+		return topazSource{}, transportClientError(err)
 	}
 	defer resp.Body.Close()
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
@@ -287,7 +287,7 @@ func (c TopazClient) uploadSource(ctx context.Context, request Request, apiKey,
 		req.Header.Set("Content-Type", topazContainerContentType(source.Container))
 		resp, err := httpClient(request.HTTPClient, c.HTTPClient).Do(req)
 		if err != nil {
-			return &ClientError{Code: "network", Message: err.Error(), Retryable: true}
+			return transportClientError(err)
 		}
 		_, _ = io.Copy(io.Discard, io.LimitReader(resp.Body, 1<<20))
 		resp.Body.Close()
@@ -353,7 +353,7 @@ func (c TopazClient) topazJSON(ctx context.Context, request Request, apiKey, met
 	}
 	resp, err := httpClient(request.HTTPClient, c.HTTPClient).Do(req)
 	if err != nil {
-		return nil, &ClientError{Code: "network", Message: err.Error(), Retryable: true}
+		return nil, transportClientError(err)
 	}
 	result, decodeErr := decodeHTTPResponse(resp)
 	if decodeErr != nil {