feat: 多班级版 v2.0 - Go后端重写 + 43轮代码审查

- 后端从 Python FastAPI 重写为 Go Gin（端口 56789）
- 多班级完全隔离
- 超级管理员独立登录
- 课代表作业管理、排行榜分项排行
- 角色加减分上下限可配置
- 家长改密功能（可开关）
- 周度/月度重置功能
- MySQL 5.7 兼容
- 43轮代码审查+全部修复
- Apache 2.0 许可证

backend-go/internal/handler/subject_handler.go

@@ -0,0 +1,152 @@
+// ===========================================
+// 多班级版班级管理系统 - Go 后端
+//
+// 开发者: Canglan
+// 联系方式: admin@sea-studio.top
+// 版权归属: Sea Network Technology Studio
+// 许可证: Apache License 2.0
+//
+// 版权所有 © Sea Network Technology Studio
+// ===========================================
+
+package handler
+
+import (
+	"github.com/gin-gonic/gin"
+
+	"hz-gitea.sea-studio.top/canglan/SharedClassManager/internal/schema"
+	"hz-gitea.sea-studio.top/canglan/SharedClassManager/internal/service"
+	"hz-gitea.sea-studio.top/canglan/SharedClassManager/pkg/response"
+)
+
+// SubjectHandler 科目管理处理器
+type SubjectHandler struct {
+	subjectService *service.SubjectService
+}
+
+// NewSubjectHandler 创建科目管理处理器
+func NewSubjectHandler(subjectService *service.SubjectService) *SubjectHandler {
+	return &SubjectHandler{subjectService: subjectService}
+}
+
+// SubjectList 科目列表
+func (h *SubjectHandler) SubjectList(c *gin.Context) {
+	var isActive *bool
+	if v := c.Query("is_active"); v == "true" {
+		b := true
+		isActive = &b
+	} else if v == "false" {
+		b := false
+		isActive = &b
+	}
+
+	result, err := h.subjectService.GetSubjects(isActive)
+	if err != nil {
+		response.InternalError(c, "获取科目列表失败")
+		return
+	}
+	response.Success(c, result, "操作成功")
+}
+
+// SubjectCreate 创建科目
+func (h *SubjectHandler) SubjectCreate(c *gin.Context) {
+	var req schema.SubjectCreateRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.BadRequest(c, "参数错误")
+		return
+	}
+
+	result, err := h.subjectService.CreateSubject(req.SubjectName, req.SubjectCode, req.SortOrder)
+	if err != nil {
+		response.InternalError(c, err.Error())
+		return
+	}
+
+	if success, _ := result["success"].(bool); !success {
+		response.BadRequest(c, result["message"].(string))
+		return
+	}
+	response.Success(c, result, "操作成功")
+}
+
+// SubjectUpdate 更新科目
+func (h *SubjectHandler) SubjectUpdate(c *gin.Context) {
+	subjectID, ok := parseID(c, "subject_id")
+	if !ok {
+		return
+	}
+
+	var req schema.SubjectUpdateRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.BadRequest(c, "参数错误")
+		return
+	}
+
+	updates := make(map[string]interface{})
+	if req.SubjectName != nil {
+		updates["subject_name"] = *req.SubjectName
+	}
+	if req.SubjectCode != nil {
+		updates["subject_code"] = *req.SubjectCode
+	}
+	if req.IsActive != nil {
+		updates["is_active"] = *req.IsActive
+	}
+	if req.SortOrder != nil {
+		updates["sort_order"] = *req.SortOrder
+	}
+
+	if err := h.subjectService.UpdateSubject(subjectID, updates); err != nil {
+		response.InternalError(c, err.Error())
+		return
+	}
+	response.SuccessWithMessage(c, "更新成功")
+}
+
+// SubjectDelete 删除科目
+func (h *SubjectHandler) SubjectDelete(c *gin.Context) {
+	subjectID, ok := parseID(c, "subject_id")
+	if !ok {
+		return
+	}
+
+	if err := h.subjectService.DeleteSubject(subjectID); err != nil {
+		response.InternalError(c, err.Error())
+		return
+	}
+	response.SuccessWithMessage(c, "删除成功")
+}
+
+// SubjectToggle 切换科目启用/禁用状态
+func (h *SubjectHandler) SubjectToggle(c *gin.Context) {
+	subjectID, ok := parseID(c, "subject_id")
+	if !ok {
+		return
+	}
+
+	var req struct {
+		IsActive bool `json:"is_active"`
+	}
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.BadRequest(c, "参数错误")
+		return
+	}
+
+	var err error
+	if req.IsActive {
+		err = h.subjectService.EnableSubject(subjectID)
+	} else {
+		err = h.subjectService.DisableSubject(subjectID)
+	}
+
+	if err != nil {
+		response.InternalError(c, err.Error())
+		return
+	}
+
+	if req.IsActive {
+		response.SuccessWithMessage(c, "科目已启用")
+	} else {
+		response.SuccessWithMessage(c, "科目已禁用")
+	}
+}