完善生图5.0的功能

backend/internal/billing/defaults.go

@@ -25,6 +25,7 @@ func DefaultBillingPriceRules() []PriceRule {
 		{ID: "base-evolink-gpt-image-2", Provider: "evolink", Capability: "image.generate", ReqKey: "gpt-image-2", Unit: UnitImage, StandardUnitPriceFen: 34, Note: "medium / 1K / 1:1 / 无参考图基准。", Source: catalogSource("https://evolink.ai/zh/gpt-image-2"), Dimensions: evolinkDimensions()},
 		{ID: "base-bailian-wan27-image-pro", Provider: "bailian", Capability: "image.generate", ReqKey: "wan2.7-image-pro", Unit: UnitImage, StandardUnitPriceFen: 50, Source: catalogSource("https://help.aliyun.com/zh/model-studio/wan2-7-image-pro")},
 		{ID: "base-seedream-5-0-pro", Provider: "seedream", Capability: "image.generate", ReqKey: Seedream50ProModel, Unit: UnitImage, StandardUnitPriceFen: 30, Note: "基础生图：1K/1.5K ¥0.30，2K ¥0.60；首张输入图免费，额外输入图 ¥0.02/张。", Source: catalogSource("https://docs.volcengine.com/docs/82379/1544106?lang=zh"), Dimensions: seedreamDimensions()},
+		{ID: "base-seedream-5-0-pro-layers", Provider: "seedream", Capability: "image.generate", ReqKey: Seedream50ProModel, Unit: UnitImage, StandardUnitPriceFen: 15, Conditions: Conditions{"layerDecomposition": true}, Priority: 10, Note: "图层拆分：≤261万像素 ¥0.15/张，>261万像素 ¥0.30/张；最多预留底图加16个图层，完成后按每张实际像素结算。", Source: catalogSource("https://docs.volcengine.com/docs/82379/1544106?lang=zh"), Dimensions: seedreamDimensions()},
 		{ID: "base-bailian-wan27-i2v-720p", Provider: "bailian", Capability: "video.generate", ReqKey: "wan2.7-i2v-2026-04-25", VariantKey: "resolution=720p", Unit: UnitVideoSecond, StandardUnitPriceFen: 60, Source: catalogSource("https://help.aliyun.com/zh/model-studio/wan2-7-i2v")},
 		{ID: "base-bailian-wan27-i2v-1080p", Provider: "bailian", Capability: "video.generate", ReqKey: "wan2.7-i2v-2026-04-25", VariantKey: "resolution=1080p", Unit: UnitVideoSecond, StandardUnitPriceFen: 100, Source: catalogSource("https://help.aliyun.com/zh/model-studio/wan2-7-i2v")},
 		{ID: "base-seedance-2-0-480p", Provider: "seedance", Capability: "video.generate", ReqKey: "doubao-seedance-2-0-260128", VariantKey: "resolution=480p", Unit: UnitVideoSecond, StandardUnitPriceFen: 46, Source: catalogSource("https://www.volcengine.com/docs/82379/1544106?lang=zh")},
@@ -46,6 +47,7 @@ func seedreamDimensions() []ParameterDimension {
 	return []ParameterDimension{{
 		Key: "size", Label: "分辨率", BaselineValue: "1.5K", DefaultValue: "1.5K",
 		Tiers: []ParameterTier{
+			{Value: "auto", Label: "自动（图层拆分）", StandardFactor: 2, MarkupMultiplier: DefaultBillingMarkupMultiplier, Enabled: true},
 			{Value: "1K", Label: "1K", StandardFactor: 1, MarkupMultiplier: DefaultBillingMarkupMultiplier, Enabled: true},
 			{Value: "1.5K", Label: "1.5K", StandardFactor: 1, MarkupMultiplier: DefaultBillingMarkupMultiplier, Enabled: true},
 			{Value: "2K", Label: "2K", StandardFactor: 2, MarkupMultiplier: DefaultBillingMarkupMultiplier, Enabled: true},
@@ -100,6 +102,18 @@ func NormalizeBillingParameters(payload map[string]any, fallback Parameters) Par
 	setNumber(out, "scale", first(input["scale"], settings["scale"]), false)
 	setText(out, "outputFormat", first(settings["outputFormat"], providerPayload["output_format"], inputSettings["outputFormat"], input["outputFormat"]))
 	setText(out, "optimizeMode", first(settings["optimizeMode"], record(providerPayload["optimize_prompt_options"])["mode"], inputSettings["optimizeMode"], input["optimizeMode"]))
+	setText(out, "creationMode", first(settings["creationMode"], inputSettings["creationMode"], input["creationMode"]))
+	if value, ok := boolean(first(settings["layerDecomposition"], providerPayload["layer_decomposition"], inputSettings["layerDecomposition"], input["layerDecomposition"])); ok {
+		out["layerDecomposition"] = value
+	}
+	if strings.EqualFold(fmt.Sprint(out["creationMode"]), "layers") {
+		out["layerDecomposition"] = true
+	}
+	if value, _ := out["layerDecomposition"].(bool); value {
+		// Seedream can return one base image plus at most sixteen layers. Reserve
+		// the documented maximum, then settle each returned image by pixel tier.
+		out["imageCount"] = float64(17)
+	}
 
 	width, widthOK := finiteNumber(first(providerPayload["width"], input["width"]))
 	height, heightOK := finiteNumber(first(providerPayload["height"], input["height"]))