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/model/notification.go

@@ -2,13 +2,15 @@ package model
 
 // 消息/通知类型常量
 const (
-	NotifyAuditApproved  = "audit_approved"
-	NotifyAuditRejected  = "audit_rejected"
-	NotifyPostApproved   = "post_approved"
-	NotifyPostRejected   = "post_rejected"
-	NotifyLevelUp        = "level_up"
-	NotifyComment        = "comment"
-	NotifyCommentReply   = "comment_reply"
+	NotifyAuditApproved   = "audit_approved"
+	NotifyAuditRejected   = "audit_rejected"
+	NotifyPostApproved    = "post_approved"
+	NotifyPostRejected    = "post_rejected"
+	NotifyLevelUp         = "level_up"
+	NotifyComment         = "comment"
+	NotifyCommentReply    = "comment_reply"
+	NotifyLikeAggregated  = "like_aggregated" // 每日聚合点赞通知
+	NotifyFollow          = "follow"           // 关注通知
 )
 
 // Notification 消息/通知模型
@@ -26,13 +28,28 @@ type Notification struct {
 
 // NotifyTypeNames 通知类型 → 中文名
 var NotifyTypeNames = map[string]string{
-	NotifyAuditApproved: "资料审核",
-	NotifyAuditRejected: "资料审核",
-	NotifyPostApproved:  "稿件审核",
-	NotifyPostRejected:  "稿件审核",
-	NotifyLevelUp:       "等级提升",
-	NotifyComment:       "评论",
-	NotifyCommentReply:  "回复",
+	NotifyAuditApproved:  "资料审核",
+	NotifyAuditRejected:  "资料审核",
+	NotifyPostApproved:   "稿件审核",
+	NotifyPostRejected:   "稿件审核",
+	NotifyLevelUp:        "等级提升",
+	NotifyComment:        "评论",
+	NotifyCommentReply:   "回复",
+	NotifyLikeAggregated: "点赞",
+	NotifyFollow:         "关注",
+}
+
+// NotifyCategory 通知类型所属分类 TAB
+var NotifyCategory = map[string]string{
+	NotifyAuditApproved:  "system",
+	NotifyAuditRejected:  "system",
+	NotifyPostApproved:   "system",
+	NotifyPostRejected:   "system",
+	NotifyLevelUp:        "system",
+	NotifyComment:        "mention",
+	NotifyCommentReply:   "mention",
+	NotifyLikeAggregated: "like",
+	NotifyFollow:         "follow",
 }
 
 // NotificationListResult 消息列表查询结果