feat(plugins): DashScope Wan3 - 新增 wan3.0 原生视频协议插件

对齐 dashscope-wan-video 风格，支持 media type+url、originPath 与 UNKNOWN 失败映射；序列化 providerOptions 供声明式校验引用。

backend/internal/protocol/manifest.go

@@ -1088,6 +1088,10 @@ func manifestRequestValues(request GenerationRequest) map[string]any {
 	output.GenerateAudio = output.GenerateAudio || request.GenerateAudio
 	output.Watermark = output.Watermark || request.Watermark
 	outputValue, _ := requestAsManifestValue(output)
+	providerOptionsValue, _ := requestAsManifestValue(request.ProviderOptions)
+	if providerOptionsValue == nil {
+		providerOptionsValue = map[string]any{}
+	}
 
 	return map[string]any{
 		"capability":      request.Capability,
@@ -1108,7 +1112,7 @@ func manifestRequestValues(request GenerationRequest) map[string]any {
 		"watermark":       request.Watermark,
 		"operation":       request.Operation,
 		"output":          outputValue,
-		"providerOptions": request.ProviderOptions,
+		"providerOptions": providerOptionsValue,
 		"extra":           request.Extra,
 	}
 }