feat(openai): 同步生图 API 支持并接入图片计费调度

- 同步 OpenAI 图片生成与编辑接口
- 接入图片请求解析、账号调度、转发与用量记录
- 接入图片计费与图片用量落库
- 限制 OAuth 生图仅支持无显式模型和尺寸的基础请求

backend/internal/server/routes/gateway.go

@@ -88,6 +88,30 @@ func RegisterGatewayRoutes(
 			}
 			h.Gateway.ChatCompletions(c)
 		})
+		gateway.POST("/images/generations", func(c *gin.Context) {
+			if getGroupPlatform(c) != service.PlatformOpenAI {
+				c.JSON(http.StatusNotFound, gin.H{
+					"error": gin.H{
+						"type":    "not_found_error",
+						"message": "Images API is not supported for this platform",
+					},
+				})
+				return
+			}
+			h.OpenAIGateway.Images(c)
+		})
+		gateway.POST("/images/edits", func(c *gin.Context) {
+			if getGroupPlatform(c) != service.PlatformOpenAI {
+				c.JSON(http.StatusNotFound, gin.H{
+					"error": gin.H{
+						"type":    "not_found_error",
+						"message": "Images API is not supported for this platform",
+					},
+				})
+				return
+			}
+			h.OpenAIGateway.Images(c)
+		})
 	}
 
 	// Gemini 原生 API 兼容层（Gemini SDK/CLI 直连）
@@ -124,6 +148,30 @@ func RegisterGatewayRoutes(
 		}
 		h.Gateway.ChatCompletions(c)
 	})
+	r.POST("/images/generations", bodyLimit, clientRequestID, opsErrorLogger, endpointNorm, gin.HandlerFunc(apiKeyAuth), requireGroupAnthropic, func(c *gin.Context) {
+		if getGroupPlatform(c) != service.PlatformOpenAI {
+			c.JSON(http.StatusNotFound, gin.H{
+				"error": gin.H{
+					"type":    "not_found_error",
+					"message": "Images API is not supported for this platform",
+				},
+			})
+			return
+		}
+		h.OpenAIGateway.Images(c)
+	})
+	r.POST("/images/edits", bodyLimit, clientRequestID, opsErrorLogger, endpointNorm, gin.HandlerFunc(apiKeyAuth), requireGroupAnthropic, func(c *gin.Context) {
+		if getGroupPlatform(c) != service.PlatformOpenAI {
+			c.JSON(http.StatusNotFound, gin.H{
+				"error": gin.H{
+					"type":    "not_found_error",
+					"message": "Images API is not supported for this platform",
+				},
+			})
+			return
+		}
+		h.OpenAIGateway.Images(c)
+	})
 
 	// Antigravity 模型列表
 	r.GET("/antigravity/models", gin.HandlerFunc(apiKeyAuth), requireGroupAnthropic, h.Gateway.AntigravityModels)