feat(admin): add comprehensive admin management system

- Add admin handlers and services for users, posts, comments, groups, and dashboard
- Implement role permission management with ability to view and update permissions
- Add database seeding for roles and Casbin permission policies
- Upgrade Casbin from v2 to v3 with GORM adapter for persistent policy storage
- Add admin-specific repository methods with filtering and pagination
- Register new admin API routes under /api/v1/admin/*

internal/model/post.go

@@ -46,9 +46,10 @@ type Post struct {
 	HotScore       float64 `json:"hot_score" gorm:"column:hot_score;default:0;index:idx_posts_hot_score_created,priority:1"`
 
 	// 置顶/锁定
-	IsPinned  bool `json:"is_pinned" gorm:"default:false"`
-	IsLocked  bool `json:"is_locked" gorm:"default:false"`
-	IsDeleted bool `json:"-" gorm:"default:false"`
+	IsPinned   bool `json:"is_pinned" gorm:"default:false"`
+	IsFeatured bool `json:"is_featured" gorm:"default:false"` // 加精
+	IsLocked   bool `json:"is_locked" gorm:"default:false"`
+	IsDeleted  bool `json:"-" gorm:"default:false"`
 
 	// 投票
 	IsVote bool `json:"is_vote" gorm:"column:is_vote;default:false"`