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/oauth/gin_context.go

@@ -0,0 +1,22 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package oauth
+
+import "github.com/gin-gonic/gin"
+
+// GetFromContext 从 Gin 请求上下文获取指定类型的值。
+func GetFromContext[T any](c *gin.Context, key string) (T, bool) {
+	value, exists := c.Get(key)
+	if !exists {
+		var zero T
+		return zero, false
+	}
+	typed, ok := value.(T)
+	return typed, ok
+}
+
+// SetToContext 设置值到 Gin 请求上下文。
+func SetToContext[T any](c *gin.Context, key string, value T) {
+	c.Set(key, value)
+}