refactor: 调整项目结构为单向依赖

backend/internal/server/middleware/auth_subject.go

@@ -0,0 +1,28 @@
+package middleware
+
+import "github.com/gin-gonic/gin"
+
+// AuthSubject is the minimal authenticated identity stored in gin context.
+// Decision: {UserID int64, Concurrency int}
+type AuthSubject struct {
+	UserID      int64
+	Concurrency int
+}
+
+func GetAuthSubjectFromContext(c *gin.Context) (AuthSubject, bool) {
+	value, exists := c.Get(string(ContextKeyUser))
+	if !exists {
+		return AuthSubject{}, false
+	}
+	subject, ok := value.(AuthSubject)
+	return subject, ok
+}
+
+func GetUserRoleFromContext(c *gin.Context) (string, bool) {
+	value, exists := c.Get(string(ContextKeyUserRole))
+	if !exists {
+		return "", false
+	}
+	role, ok := value.(string)
+	return role, ok
+}