feat: 实现关注系统 + 通知侧边栏分类 TAB + 点赞聚合通知

- 新增关注系统：UserFollow 模型、FollowService（toggle/status/列表隐私控制）
- User 新增 FollowersCount/FollowingCount/FollowListPublic/NotifyPrefs 字段
- Space 页面增加四态关注按钮（关注/已关注/回关/已互粉）+ 粉丝/关注数链接
- 新增 /space/:uid/followers 和 /space/:uid/following 列表页
- 新增 NotifyFollow/NotifyLikeAggregated 通知类型
- ReactionService 点赞时写入 daily_like_summary，访问时生成聚合通知
- FollowService 关注时触发 NotifyFollow 通知
- 消息中心侧边栏升级为分类 TAB（全部/系统通知/@艾特/点赞/关注）
- NotificationService 新增 ListByCategory 按分类分页查询

internal/controller/follow_controller.go

@@ -0,0 +1,188 @@
+package controller
+
+import (
+	"net/http"
+	"strconv"
+
+	"metazone.cc/metalab/internal/common"
+	"metazone.cc/metalab/internal/model"
+	"metazone.cc/metalab/internal/service"
+
+	"github.com/gin-gonic/gin"
+)
+
+// FollowController 关注 API 控制器
+type FollowController struct {
+	followSvc followUseCase
+}
+
+// NewFollowController 构造函数
+func NewFollowController(followSvc followUseCase) *FollowController {
+	return &FollowController{followSvc: followSvc}
+}
+
+// Toggle 切换关注 POST /api/users/:uid/follow
+func (fc *FollowController) Toggle(c *gin.Context) {
+	uid, _, ok := common.GetGinUser(c)
+	if !ok {
+		common.Error(c, http.StatusUnauthorized, "请先登录")
+		return
+	}
+
+	targetUID, err := strconv.ParseUint(c.Param("uid"), 10, 64)
+	if err != nil {
+		common.Error(c, http.StatusBadRequest, "无效的用户ID")
+		return
+	}
+
+	isFollowing, err := fc.followSvc.Toggle(uid, uint(targetUID))
+	if err != nil {
+		if err.Error() == "不能关注自己" {
+			common.Error(c, http.StatusBadRequest, err.Error())
+			return
+		}
+		common.Error(c, http.StatusInternalServerError, "操作失败")
+		return
+	}
+
+	// 获取最新状态
+	status, _ := fc.followSvc.GetStatus(uid, uint(targetUID))
+
+	common.Ok(c, gin.H{
+		"is_following": isFollowing,
+		"status":       status,
+	})
+}
+
+// GetStatus 查询关注关系 GET /api/users/:uid/follow-status
+func (fc *FollowController) GetStatus(c *gin.Context) {
+	targetUID, err := strconv.ParseUint(c.Param("uid"), 10, 64)
+	if err != nil {
+		common.Error(c, http.StatusBadRequest, "无效的用户ID")
+		return
+	}
+
+	uid, _, _ := common.GetGinUser(c) // 允许未登录（返回全是 false）
+
+	status, err := fc.followSvc.GetStatus(uid, uint(targetUID))
+	if err != nil {
+		common.Error(c, http.StatusInternalServerError, "查询失败")
+		return
+	}
+
+	common.Ok(c, status)
+}
+
+// Followers 粉丝列表 GET /api/users/:uid/followers
+func (fc *FollowController) Followers(c *gin.Context) {
+	targetUID, err := strconv.ParseUint(c.Param("uid"), 10, 64)
+	if err != nil {
+		common.Error(c, http.StatusBadRequest, "无效的用户ID")
+		return
+	}
+
+	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
+	pageSize, _ := strconv.Atoi(c.DefaultQuery("page_size", "20"))
+
+	uid, _, _ := common.GetGinUser(c) // 允许未登录
+
+	result, err := fc.followSvc.ListFollowers(uint(targetUID), uid, page, pageSize)
+	if err != nil {
+		common.Error(c, http.StatusInternalServerError, "查询失败")
+		return
+	}
+
+	common.Ok(c, result)
+}
+
+// Following 关注列表 GET /api/users/:uid/following
+func (fc *FollowController) Following(c *gin.Context) {
+	targetUID, err := strconv.ParseUint(c.Param("uid"), 10, 64)
+	if err != nil {
+		common.Error(c, http.StatusBadRequest, "无效的用户ID")
+		return
+	}
+
+	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
+	pageSize, _ := strconv.Atoi(c.DefaultQuery("page_size", "20"))
+
+	uid, _, _ := common.GetGinUser(c)
+
+	result, err := fc.followSvc.ListFollowing(uint(targetUID), uid, page, pageSize)
+	if err != nil {
+		common.Error(c, http.StatusInternalServerError, "查询失败")
+		return
+	}
+
+	common.Ok(c, result)
+}
+
+// FollowPageController 关注/粉丝页面控制器
+type FollowPageController struct {
+	followSvc followUseCase
+}
+
+// NewFollowPageController 构造函数
+func NewFollowPageController(followSvc followUseCase) *FollowPageController {
+	return &FollowPageController{followSvc: followSvc}
+}
+
+// FollowersPage 粉丝列表页面
+func (fpc *FollowPageController) FollowersPage(c *gin.Context) {
+	targetUID, err := strconv.ParseUint(c.Param("uid"), 10, 64)
+	if err != nil {
+		common.Error(c, http.StatusBadRequest, "无效的用户ID")
+		return
+	}
+
+	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
+
+	uid, _, _ := common.GetGinUser(c)
+	result, err := fpc.followSvc.ListFollowers(uint(targetUID), uid, page, 20)
+	if err != nil {
+		result = &service.FollowListResult{Items: []model.UserFollow{}, Total: 0}
+	}
+
+	c.HTML(http.StatusOK, "follow/followers.html", common.BuildPageData(c, gin.H{
+		"Title":      "粉丝列表",
+		"ExtraCSS":   "/static/css/follow.css",
+		"Result":     result,
+		"TargetUID":  targetUID,
+		"Page":     result.Page,
+		"TotalPages": result.TotalPages,
+		"HasPrev":    result.Page > 1,
+		"HasNext":    result.Page < result.TotalPages,
+		"PrevPage":   result.Page - 1,
+		"NextPage":   result.Page + 1,
+	}))
+}
+
+// FollowingPage 关注列表页面
+func (fpc *FollowPageController) FollowingPage(c *gin.Context) {
+	targetUID, err := strconv.ParseUint(c.Param("uid"), 10, 64)
+	if err != nil {
+		common.Error(c, http.StatusBadRequest, "无效的用户ID")
+		return
+	}
+
+	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
+
+	uid, _, _ := common.GetGinUser(c)
+	result, err := fpc.followSvc.ListFollowing(uint(targetUID), uid, page, 20)
+	if err != nil {
+		result = &service.FollowListResult{Items: []model.UserFollow{}, Total: 0}
+	}
+
+	c.HTML(http.StatusOK, "follow/following.html", common.BuildPageData(c, gin.H{
+		"Title":      "关注列表",
+		"ExtraCSS":   "/static/css/follow.css",
+		"Result":     result,
+		"TargetUID":  targetUID,
+		"Page":       result.Page,
+		"TotalPages": result.TotalPages,
+		"HasPrev":    result.Page > 1,
+		"HasNext":    result.Page < result.TotalPages,
+		"PrevPage":   result.Page - 1,
+		"NextPage":   result.Page + 1,
+	}))
+}