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/admin/updater/restart_windows.go

@@ -0,0 +1,12 @@
+//go:build windows
+
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package updater
+
+import "errors"
+
+func replaceAndRestart(_, _ string) error {
+	return errors.New(errAutomaticUpgradeBlocked)
+}