feat(inference): 实现文生图与图片编辑 API 调用，新增管线与编辑 HTTP 端点，JWT 认证中间件

- inference.go: GenerateImages 改为 API 优先（callImageGenAPI），无 key 回退 mock；新增 EditImages/callImageEditAPI（multipart 上传编辑）；提取 parseImageResponse 共享响应解析
- handler/generate.go: POST /api/v1/generate 触发生成管线，返回 base64 图片
- handler/edit.go: POST /api/v1/images/edit 图片编辑端点
- mildware/auth.go: JWT Bearer token 认证中间件
- main.go: 路由拆分公开/认证组，generate 与 images/edit 需鉴权

backend/internal/mildware/auth.go

@@ -0,0 +1,48 @@
+package mildware
+
+import (
+	"net/http"
+	"strings"
+
+	"gen2d/internal/model"
+
+	"github.com/gin-gonic/gin"
+	"github.com/golang-jwt/jwt/v5"
+)
+
+// AuthMiddleware 返回 JWT 认证中间件，校验 Bearer token 并注入 userID 到上下文。
+func AuthMiddleware(jwtSecret string) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		authHeader := c.GetHeader("Authorization")
+		if authHeader == "" {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, model.Fail(http.StatusUnauthorized, "未提供认证令牌"))
+			return
+		}
+
+		tokenString := strings.TrimPrefix(authHeader, "Bearer ")
+		if tokenString == authHeader {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, model.Fail(http.StatusUnauthorized, "认证格式错误，需为 Bearer <token>"))
+			return
+		}
+
+		token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
+			return []byte(jwtSecret), nil
+		})
+		if err != nil || !token.Valid {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, model.Fail(http.StatusUnauthorized, "令牌无效或已过期"))
+			return
+		}
+
+		claims, ok := token.Claims.(jwt.MapClaims)
+		if !ok {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, model.Fail(http.StatusUnauthorized, "令牌解析失败"))
+			return
+		}
+
+		if sub, ok := claims["sub"]; ok {
+			c.Set("userID", sub)
+		}
+
+		c.Next()
+	}
+}