refactor(repository): 收敛 model/repository 分层为唯一持久化入口

将 OpenFlare 与平台业务的数据访问从 model 与 apps 直连迁入 repository，
model 仅保留实体与无 IO 规则；补充 code-check 架构守卫与开发规范。

internal/repository/system_config.go

@@ -18,14 +18,7 @@ import (
 	"github.com/Rain-kl/Wavelet/pkg/cache/ram"
 )
 
-const (
-	configTypeSystem                = "system"
-	errDatabaseNotInitialized       = "database not initialized"
-	errConfigIntParseFailed         = "配置 %s 的值 '%s' 无法转换为整数: %w"
-	errConfigDecimalParseFailed     = "配置 %s 的值 '%s' 无法转换为decimal: %w"
-	errConfigBoolParseFailed        = "配置 %s 的值 '%s' 无法转换为布尔值: %w"
-	errParseMenuDisplayConfigFailed = "解析目录显示配置失败: %w"
-)
+const configTypeSystem = "system"
 
 // PreheatSystemConfigs loads all system configs from database.
 // This function strictly performs database read and does not perform any cache read or write operations.