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/errors.go

@@ -0,0 +1,34 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package apiutil
+
+import (
+	"errors"
+
+	"github.com/Rain-kl/Wavelet/internal/common/response"
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+)
+
+// AbortNotFoundIfMissing maps gorm.ErrRecordNotFound to 404; other errors to 400.
+func AbortNotFoundIfMissing(c *gin.Context, err error, notFoundMsg string) bool {
+	if err == nil {
+		return false
+	}
+	if errors.Is(err, gorm.ErrRecordNotFound) {
+		response.AbortNotFound(c, notFoundMsg)
+		return true
+	}
+	response.AbortBadRequest(c, err.Error())
+	return true
+}
+
+// AbortBadRequestOnError writes a 400 for any non-nil error.
+func AbortBadRequestOnError(c *gin.Context, err error) bool {
+	if err == nil {
+		return false
+	}
+	response.AbortBadRequest(c, err.Error())
+	return true
+}