refactor: remove Gorse integration and implement HotRank feature

- Removed Gorse-related configurations, handlers, and dependencies from the codebase.
- Introduced HotRank feature with configuration options for ranking posts based on recent activity.
- Updated application structure to support HotRank processing, including new caching mechanisms and database interactions.
- Cleaned up related DTOs and repository methods to reflect the removal of Gorse and the addition of HotRank functionality.

internal/model/init.go

@@ -163,6 +163,11 @@ func autoMigrate(db *gorm.DB) error {
 		return err
 	}
 
+	// AutoMigrate 不会删除列：清理已废弃的 posts.hot_score
+	if err := dropPostsHotScoreColumnIfExists(db); err != nil {
+		return fmt.Errorf("drop legacy posts.hot_score: %w", err)
+	}
+
 	// 初始化角色种子数据
 	if err := seedRoles(db); err != nil {
 		return fmt.Errorf("failed to seed roles: %w", err)
@@ -176,6 +181,24 @@ func autoMigrate(db *gorm.DB) error {
 	return nil
 }
 
+// postWithHotScore 仅用于 Migrator 检测/删除旧列（Post 模型已移除 HotScore）
+type postWithHotScore struct {
+	HotScore float64 `gorm:"column:hot_score"`
+}
+
+func (postWithHotScore) TableName() string { return "posts" }
+
+func dropPostsHotScoreColumnIfExists(db *gorm.DB) error {
+	m := db.Migrator()
+	if !m.HasTable(&Post{}) {
+		return nil
+	}
+	if !m.HasColumn(&postWithHotScore{}, "HotScore") {
+		return nil
+	}
+	return m.DropColumn(&postWithHotScore{}, "HotScore")
+}
+
 // seedRoles 初始化角色种子数据
 func seedRoles(db *gorm.DB) error {
 	// 检查是否已有角色数据