refactor: 移除 infrastructure 目录 (#108)

* refactor: 迁移初始化 db 和 redis 到 repository

* refactor: 迁移 errors 到 pkg

backend/internal/setup/setup.go

@@ -11,7 +11,7 @@ import (
 	"strconv"
 	"time"
 
-	"github.com/Wei-Shaw/sub2api/internal/infrastructure"
+	"github.com/Wei-Shaw/sub2api/internal/repository"
 	"github.com/Wei-Shaw/sub2api/internal/service"
 
 	_ "github.com/lib/pq"
@@ -262,7 +262,7 @@ func initializeDatabase(cfg *SetupConfig) error {
 
 	migrationCtx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
 	defer cancel()
-	return infrastructure.ApplyMigrations(migrationCtx, db)
+	return repository.ApplyMigrations(migrationCtx, db)
 }
 
 func createAdminUser(cfg *SetupConfig) error {