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/config/external.go

@@ -1,15 +1,17 @@
 package config
 
-// GorseConfig Gorse 推荐系统配置
-type GorseConfig struct {
-	Address         string `mapstructure:"address"`
-	APIKey          string `mapstructure:"api_key"`
-	Enabled         bool   `mapstructure:"enabled"`
-	Dashboard       string `mapstructure:"dashboard"`
-	ImportPassword  string `mapstructure:"import_password"`
-	EmbeddingAPIKey string `mapstructure:"embedding_api_key"`
-	EmbeddingURL    string `mapstructure:"embedding_url"`
-	EmbeddingModel  string `mapstructure:"embedding_model"`
+// HotRankConfig 热门榜定时重算（仅 Redis ZSET + 分层缓存中的 Top ID 列表，不写库）
+type HotRankConfig struct {
+	Enabled                bool `mapstructure:"enabled"`
+	RefreshIntervalSeconds int  `mapstructure:"refresh_interval_seconds"`
+	// TopN 写入缓存的热门条数（ZSET 与 top_ids 列表长度上限）
+	TopN int `mapstructure:"top_n"`
+	// RecentWindowHours 候选池：该时间窗内新发的帖子 ID 会参与本轮重算
+	RecentWindowHours int `mapstructure:"recent_window_hours"`
+	// RecentFetchLimit 时间窗内最多拉取的帖子 ID 数（按 created_at 倒序）
+	RecentFetchLimit int `mapstructure:"recent_fetch_limit"`
+	// CandidateCap 候选 ID 合并后的上限（上届 Top + 新帖去重后截断）
+	CandidateCap int `mapstructure:"candidate_cap"`
 }
 
 // OpenAIConfig OpenAI 配置