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/apps/openflare/config_version/errs.go

@@ -0,0 +1,12 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package config_version
+
+const (
+	errNoActiveVersion       = "当前没有激活版本"
+	errNoEnabledRoutes       = "没有可发布的启用规则"
+	errNoChangesToPublish    = "当前规则没有变更，不能重复发布"
+	errVersionConflict       = "版本号生成冲突，请重试"
+	errInvalidSnapshotFormat = "历史版本快照格式不合法"
+)