chore: 初始提交 Fonu 1.0.2

- 公网反代：Nginx 状态卡片（版本 / 运行状态 / 配置校验 / 端口监听）
- 部署设置第一、二梯队（HTTPS 开关、安全头、限流、连接数、仅中国大陆 IP）
- 隧道检测兼容 frps v0.68 / v0.71（V2 与旧版端点）
- 恢复被清空的 internal/frp/store.go、internal/api/ddns_handler.go、web/src/views/DdnsView.vue

internal/notify/smtp.go

@@ -0,0 +1,90 @@
+package notify
+
+import (
+	"crypto/tls"
+	"fmt"
+	"net/smtp"
+	"strings"
+)
+
+func SendEmail(cfg RuntimeConfig, title, message string) error {
+	if strings.TrimSpace(cfg.Email.Host) == "" {
+		return fmt.Errorf("SMTP 主机未配置")
+	}
+	if len(cfg.Email.To) == 0 {
+		return fmt.Errorf("收件人未配置")
+	}
+	if strings.TrimSpace(cfg.SMTPPassword) == "" && strings.TrimSpace(cfg.Email.Username) != "" {
+		return fmt.Errorf("SMTP 密码未配置")
+	}
+
+	from := strings.TrimSpace(cfg.Email.From)
+	if from == "" {
+		from = strings.TrimSpace(cfg.Email.Username)
+	}
+	if from == "" {
+		return fmt.Errorf("发件人未配置")
+	}
+
+	body := buildMailBody(from, cfg.Email.To, title, message)
+	addr := fmt.Sprintf("%s:%d", cfg.Email.Host, cfg.Email.Port)
+	auth := smtp.PlainAuth("", cfg.Email.Username, cfg.SMTPPassword, cfg.Email.Host)
+
+	if cfg.Email.Port == 465 {
+		return sendSMTPS(addr, cfg.Email.Host, auth, from, cfg.Email.To, body)
+	}
+	return smtp.SendMail(addr, auth, from, cfg.Email.To, body)
+}
+
+func buildMailBody(from string, to []string, title, message string) []byte {
+	headers := []string{
+		"From: " + from,
+		"To: " + strings.Join(to, ", "),
+		"Subject: " + title,
+		"MIME-Version: 1.0",
+		"Content-Type: text/plain; charset=UTF-8",
+	}
+	bodyText := strings.TrimSpace(message)
+	if bodyText == "" {
+		bodyText = title
+	}
+	return []byte(strings.Join(headers, "\r\n") + "\r\n\r\n" + bodyText + "\r\n")
+}
+
+func sendSMTPS(addr, host string, auth smtp.Auth, from string, to []string, body []byte) error {
+	tlsCfg := &tls.Config{ServerName: host}
+	conn, err := tls.Dial("tcp", addr, tlsCfg)
+	if err != nil {
+		return err
+	}
+	client, err := smtp.NewClient(conn, host)
+	if err != nil {
+		return err
+	}
+	defer client.Close()
+
+	if auth != nil {
+		if err := client.Auth(auth); err != nil {
+			return err
+		}
+	}
+	if err := client.Mail(from); err != nil {
+		return err
+	}
+	for _, rcpt := range to {
+		if err := client.Rcpt(strings.TrimSpace(rcpt)); err != nil {
+			return err
+		}
+	}
+	writer, err := client.Data()
+	if err != nil {
+		return err
+	}
+	if _, err := writer.Write(body); err != nil {
+		return err
+	}
+	if err := writer.Close(); err != nil {
+		return err
+	}
+	return client.Quit()
+}