```

feat(base): 添加邮箱注册码功能及用户注册接口

- 在 `sessionManager` 中新增邮件注册码缓存管理实例和相关方法
- 实现生成、保存、验证、删除邮件注册码的逻辑
- 新增 `/reg` 和 `/email` 接口用于用户注册和发送验证码
- 引入 `golang-lru` 依赖以支持限流缓存功能
- 调整包导入顺序，优化代码结构
```

common/utils/golang-lru-main/README.md

@@ -0,0 +1,79 @@
+golang-lru
+==========
+
+This provides the `lru` package which implements a fixed-size
+thread safe LRU cache. It is based on the cache in Groupcache.
+
+Documentation
+=============
+
+Full docs are available on [Go Packages](https://pkg.go.dev/github.com/hashicorp/golang-lru/v2)
+
+LRU cache example
+=================
+
+```go
+package main
+
+import (
+	"fmt"
+	"github.com/hashicorp/golang-lru/v2"
+)
+
+func main() {
+	l, _ := lru.New[int, any](128)
+	for i := 0; i < 256; i++ {
+		l.Add(i, nil)
+	}
+	if l.Len() != 128 {
+		panic(fmt.Sprintf("bad len: %v", l.Len()))
+	}
+}
+```
+
+Expirable LRU cache example
+===========================
+
+```go
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/hashicorp/golang-lru/v2/expirable"
+)
+
+func main() {
+	// make cache with 10ms TTL and 5 max keys
+	cache := expirable.NewLRU[string, string](5, nil, time.Millisecond*10)
+
+
+	// set value under key1.
+	cache.Add("key1", "val1")
+
+	// get value under key1
+	r, ok := cache.Get("key1")
+
+	// check for OK value
+	if ok {
+		fmt.Printf("value before expiration is found: %v, value: %q\n", ok, r)
+	}
+
+	// wait for cache to expire
+	time.Sleep(time.Millisecond * 12)
+
+	// get value under key1 after key expiration
+	r, ok = cache.Get("key1")
+	fmt.Printf("value after expiration is found: %v, value: %q\n", ok, r)
+
+	// set value under key2, would evict old entry because it is already expired.
+	cache.Add("key2", "val2")
+
+	fmt.Printf("Cache len: %d\n", cache.Len())
+	// Output:
+	// value before expiration is found: true, value: "val1"
+	// value after expiration is found: false, value: ""
+	// Cache len: 1
+}
+```