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/apiutil/routes.go

@@ -0,0 +1,19 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package apiutil
+
+import (
+	"strings"
+
+	"github.com/gin-gonic/gin"
+)
+
+// RegisterCollection registers a collection endpoint on both "" and "/" so requests
+// work with or without a trailing slash.
+func RegisterCollection(route *gin.RouterGroup, method string, handlers ...gin.HandlerFunc) {
+	route.Handle(method, "/", handlers...)
+	if !strings.HasSuffix(route.BasePath(), "/") {
+		route.Handle(method, "", handlers...)
+	}
+}