fix(邮件发送): 适配 MailerSend SMTP 并迁移基础设施至 1Panel

Motivation:
将通知服务部署到 1Panel 生产环境，集成 MailerSend 邮件服务，修复 SMTP 协议中 MAIL FROM 命令因携带显示名而导致的发送失败问题。

Changes:

* 修复 SMTP MAIL FROM 命令传入带显示名的完整地址导致发送失败的问题，新增 extractEmailAddr 提取裸地址
* 更新 SMTP 配置为 MailerSend 真实凭证，From 地址适配其域名验证要求
* 移除 docker-compose 中内置的 MySQL/Redis 服务，改为依赖外部 1Panel 基础设施
* 更新环境变量为生产环境实际凭据

internal/adapter/email.go

@@ -91,7 +91,9 @@ func (s *EmailSender) authAndSend(client *smtp.Client, to []string, msg []byte)
 		}
 	}
 
-	if err := client.Mail(s.cfg.From); err != nil {
+	// MAIL FROM must be a bare address; display names like "Name <a@b.c>" are invalid here.
+	fromAddr := extractEmailAddr(s.cfg.From)
+	if err := client.Mail(fromAddr); err != nil {
 		return fmt.Errorf("mail: %w", err)
 	}
 	for _, recipient := range to {
@@ -121,3 +123,13 @@ func buildEmail(from string, to []string, subject, body string) []byte {
 	sb.WriteString(body)
 	return []byte(sb.String())
 }
+
+// extractEmailAddr returns the bare address from "Name <addr@host>" or the original string.
+func extractEmailAddr(from string) string {
+	start := strings.LastIndex(from, "<")
+	end := strings.LastIndex(from, ">")
+	if start >= 0 && end > start {
+		return strings.TrimSpace(from[start+1 : end])
+	}
+	return strings.TrimSpace(from)
+}