refactor(structure): group platform, infra, and shared packages

Reorganize internal packages into platform/infra/shared layers and update
imports, docs, and seed-count tests to match current system configs.

internal/infra/task/scheduler/errs.go

@@ -0,0 +1,9 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+// Package scheduler 提供定时任务调度功能
+package scheduler
+
+const (
+	errLoadLocationFailed = "failed to load location: %w"
+)