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/websocket/common.go

@@ -0,0 +1,26 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package websocket
+
+import (
+	"net/http"
+
+	"github.com/gorilla/websocket"
+)
+
+const (
+	messageTypePing   = "ping"
+	messageTypePong   = "pong"
+	messageTypeNotify = "notify"
+)
+
+// Message is a JSON-framed websocket payload.
+type Message struct {
+	Type    string `json:"type"`
+	Payload any    `json:"payload,omitempty"`
+}
+
+var upgrader = websocket.Upgrader{
+	CheckOrigin: func(_ *http.Request) bool { return true },
+}