refactor(repo): consolidate openflare-server to root and move subprojects to internal/apps

- Merge all files inside openflare-server to the repository root directory.
- Relocate agent, relay, and flared subprojects from internal/ to internal/apps/.
- Combine docker-compose files and update build context paths to root.
- Update GitHub workflows and Dockerfiles to refer to new directories and package names.
- Rewrite Go package imports across all files.
- Resolve database renew test race condition and clean up docs.

internal/task/constants.go

@@ -0,0 +1,14 @@
+// Copyright 2025 linux.do
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+// Package task 定义异步任务类型与调度常量
+package task
+
+// 任务队列名称
+const (
+	QueueDefault = "default"
+)
+
+// DefaultMaxRetry 任务默认最大重试次数
+const DefaultMaxRetry = 3