feat: 收件箱功能新增按回车查看详情面板

- 添加邮件详情面板显示（主题、发件人、收件人、抄送、账户、时间、正文）
- 优化邮件列表卡片样式，增加选中高亮效果
- 窗口宽度 >= 80 时启用双面板布局，左侧列表右侧详情
- 简化依赖包，从 charm.land 使用统一导入路径
- 删除未使用的 golangci/goreleaser 配置文件

imap.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"strings"
 	"time"
 
 	imap "github.com/BrianLeishman/go-imap"
@@ -193,3 +194,144 @@ func sortEmailsByDate(emails []ReceivedEmail) {
 		}
 	}
 }
+
+type EmailDetail struct {
+	UID       uint32
+	From      string
+	FromName  string
+	To        string
+	Cc        string
+	Subject   string
+	Date      time.Time
+	TextBody  string
+	HTMLBody  string
+	Account   string
+	AccountID string
+}
+
+func FetchEmailDetailByUID(accountID string, uid uint32) (*EmailDetail, error) {
+	account, err := GetAccountByID(accountID)
+	if err != nil {
+		return nil, err
+	}
+
+	if account.IMAP.Host == "" {
+		return nil, fmt.Errorf("IMAP host not configured for account: %s", account.Email)
+	}
+
+	port := account.IMAP.Port
+	if port == 0 {
+		port = 993
+	}
+
+	username := account.IMAP.Username
+	if username == "" {
+		username = account.Email
+	}
+
+	m, err := imap.New(username, account.IMAP.Password, account.IMAP.Host, port)
+	if err != nil {
+		return nil, fmt.Errorf("failed to connect to IMAP server: %w", err)
+	}
+	defer m.Close()
+
+	if account.CheckID != nil && *account.CheckID {
+		info := ProjectConfig.Info
+		idCmd := fmt.Sprintf("ID (\"name\" \"%s\" \"version\" \"%s\" \"vendor\" \"%s\")",
+			info.Name, info.Version, info.Vendor)
+		_, err := m.Exec(idCmd, false, 0, func(line []byte) error {
+			return nil
+		})
+		if err != nil {
+			fmt.Printf("WARNING: failed to send IMAP ID: %v\n", err)
+		}
+
+		m.Exec("NOOP", false, 0, nil)
+	}
+
+	err = m.SelectFolder("INBOX")
+	if err != nil {
+		return nil, fmt.Errorf("failed to select inbox: %w", err)
+	}
+
+	emails, err := m.GetEmails(int(uid))
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch email: %w", err)
+	}
+
+	if len(emails) == 0 {
+		return nil, fmt.Errorf("email not found")
+	}
+
+	var email imap.Email
+	found := false
+	for i := range emails {
+		if emails[i] != nil {
+			email = *emails[i]
+			found = true
+			break
+		}
+	}
+
+	if !found {
+		return nil, fmt.Errorf("email not found or has been removed")
+	}
+
+	accountName := getEmailProviderName(account.Email)
+	accountIDName := account.Email
+	if account.Name != "" {
+		accountName = account.Name
+		accountIDName = account.Name
+	}
+
+	var fromName string
+	var fromAddr string
+	if email.From != nil {
+		for name, addr := range email.From {
+			fromName = name
+			fromAddr = addr
+			break
+		}
+	}
+
+	var toList []string
+	if email.To != nil {
+		for name, addr := range email.To {
+			if name != "" {
+				toList = append(toList, fmt.Sprintf("%s <%s>", name, addr))
+			} else {
+				toList = append(toList, addr)
+			}
+		}
+	}
+
+	var ccList []string
+	if email.CC != nil {
+		for name, addr := range email.CC {
+			if name != "" {
+				ccList = append(ccList, fmt.Sprintf("%s <%s>", name, addr))
+			} else {
+				ccList = append(ccList, addr)
+			}
+		}
+	}
+
+	fromStr := fromAddr
+	if fromName != "" {
+		fromStr = fmt.Sprintf("%s <%s>", fromName, fromAddr)
+	}
+
+	return &EmailDetail{
+		UID:       uint32(email.UID),
+		From:      fromStr,
+		FromName:  fromName,
+		To:        strings.Join(toList, ", "),
+		Cc:        strings.Join(ccList, ", "),
+		Subject:   email.Subject,
+		Date:      email.Sent,
+		TextBody:  email.Text,
+		HTMLBody:  email.HTML,
+		Account:   accountName,
+		AccountID: accountIDName,
+	}, nil
+}