feat(mail): 支持发件人名称展示与存储

- 为邮件消息新增 `fromName` 字段，并同步扩展数据库迁移、API 类型与前后端查询/入库逻辑。
- 解析入站邮件时提取并保存发件人名称，发信时将邮箱显示名写入 MIME `From` 头。
- 邮件列表、详情、通知与引用内容改为优先展示发件人名称，提升可读性。

apps/api/internal/app/mime.go

@@ -10,6 +10,7 @@ import (
 	"mime"
 	"mime/multipart"
 	"net"
+	netmail "net/mail"
 	"net/smtp"
 	"net/textproto"
 	"strings"
@@ -20,6 +21,7 @@ const smtpSessionTimeout = 45 * time.Second
 
 type MIMEMessage struct {
 	From        string
+	FromName    string
 	To          []string
 	CC          []string
 	BCC         []string
@@ -38,7 +40,7 @@ func BuildMIME(m MIMEMessage) ([]byte, error) {
 			fmt.Fprintf(&buf, "%s: %s\r\n", k, v)
 		}
 	}
-	writeHeader("From", m.From)
+	writeHeader("From", formatAddressHeader(m.FromName, m.From))
 	writeHeader("To", strings.Join(m.To, ", "))
 	writeHeader("Cc", strings.Join(m.CC, ", "))
 	writeHeader("Subject", mime.QEncoding.Encode("utf-8", m.Subject))
@@ -104,6 +106,15 @@ func BuildMIME(m MIMEMessage) ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
+func formatAddressHeader(name, address string) string {
+	address = strings.TrimSpace(address)
+	name = strings.TrimSpace(name)
+	if address == "" || name == "" || strings.EqualFold(name, address) {
+		return address
+	}
+	return (&netmail.Address{Name: name, Address: address}).String()
+}
+
 func textprotoMIMEHeader(values map[string]string) textproto.MIMEHeader {
 	h := textproto.MIMEHeader{}
 	for k, v := range values {