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/persistence/errs.go

@@ -0,0 +1,12 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package db
+
+const (
+	errRedisHashSetFailed    = "failed to set redis hash: %w"
+	errRedisHashDeleteFailed = "failed to delete redis hash field: %w"
+	errUnmarshalDataFailed   = "failed to unmarshal data: %w"
+	errMarshalDataFailed     = "failed to marshal data: %w"
+	errRedisKeySetFailed     = "failed to set redis key: %w"
+)