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/push/custom_events/register.go

@@ -0,0 +1,17 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package custom_events
+
+import (
+	"github.com/Rain-kl/Wavelet/internal/apps/admin/push"
+	"github.com/Rain-kl/Wavelet/internal/listener"
+)
+
+// Register wires push notification handlers for domain events and registers
+// built-in event metadata. Must be called once during application bootstrap
+// before push.SyncEvents.
+func Register() {
+	push.RegisterBuiltInEvent(AdminLogin)
+	listener.OnAdminLoggedIn(handleAdminLogin)
+}