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/middleware/security_headers.go

@@ -96,7 +96,8 @@ func isAPIRoutePath(c *gin.Context) bool {
 	return strings.HasPrefix(path, "/v1/") ||
 		strings.HasPrefix(path, "/v1beta/") ||
 		strings.HasPrefix(path, "/antigravity/") ||
-		strings.HasPrefix(path, "/responses")
+		strings.HasPrefix(path, "/responses") ||
+		strings.HasPrefix(path, "/images")
 }
 
 // enhanceCSPPolicy ensures the CSP policy includes nonce support, Cloudflare Insights,

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)

backend/internal/server/routes/gateway_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/handler"
 	servermiddleware "github.com/Wei-Shaw/sub2api/internal/server/middleware"
+	"github.com/Wei-Shaw/sub2api/internal/service"
 	"github.com/gin-gonic/gin"
 	"github.com/stretchr/testify/require"
 )
@@ -24,6 +25,11 @@ func newGatewayRoutesTestRouter() *gin.Engine {
 			OpenAIGateway: &handler.OpenAIGatewayHandler{},
 		},
 		servermiddleware.APIKeyAuthMiddleware(func(c *gin.Context) {
+			groupID := int64(1)
+			c.Set(string(servermiddleware.ContextKeyAPIKey), &service.APIKey{
+				GroupID: &groupID,
+				Group:   &service.Group{Platform: service.PlatformOpenAI},
+			})
 			c.Next()
 		}),
 		nil,
@@ -48,3 +54,21 @@ func TestGatewayRoutesOpenAIResponsesCompactPathIsRegistered(t *testing.T) {
 		require.NotEqual(t, http.StatusNotFound, w.Code, "path=%s should hit OpenAI responses handler", path)
 	}
 }
+
+func TestGatewayRoutesOpenAIImagesPathsAreRegistered(t *testing.T) {
+	router := newGatewayRoutesTestRouter()
+
+	for _, path := range []string{
+		"/v1/images/generations",
+		"/v1/images/edits",
+		"/images/generations",
+		"/images/edits",
+	} {
+		req := httptest.NewRequest(http.MethodPost, path, strings.NewReader(`{"model":"gpt-image-2","prompt":"draw a cat"}`))
+		req.Header.Set("Content-Type", "application/json")
+		w := httptest.NewRecorder()
+
+		router.ServeHTTP(w, req)
+		require.NotEqual(t, http.StatusNotFound, w.Code, "path=%s should hit OpenAI images handler", path)
+	}
+}