fix(PROJ-30): imapclient.New — Rueckgabewert an go-imap/v2 beta.8 API anpassen

imapclient.New gibt in beta.8 nur *Client zurueck (kein error).
Alle drei Aufrufe in Connect() korrigiert.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/imap/client.go

@@ -62,11 +62,7 @@ func Connect(host string, port int, tlsMode string) (*Conn, error) {
 		if err != nil {
 			return nil, fmt.Errorf("imap connect ssl: %w", err)
 		}
-		c, err := imapclient.New(raw, nil)
-		if err != nil {
-			raw.Close()
-			return nil, fmt.Errorf("imap client ssl: %w", err)
-		}
+		c := imapclient.New(raw, nil)
 		return &Conn{Client: c, raw: raw}, nil
 
 	case "starttls":
@@ -74,13 +70,9 @@ func Connect(host string, port int, tlsMode string) (*Conn, error) {
 		if err != nil {
 			return nil, fmt.Errorf("imap connect starttls: %w", err)
 		}
-		c, err := imapclient.New(raw, &imapclient.Options{
+		c := imapclient.New(raw, &imapclient.Options{
 			TLSConfig: &tls.Config{ServerName: host},
 		})
-		if err != nil {
-			raw.Close()
-			return nil, fmt.Errorf("imap client starttls: %w", err)
-		}
 		return &Conn{Client: c, raw: raw}, nil
 
 	case "none":
@@ -88,11 +80,7 @@ func Connect(host string, port int, tlsMode string) (*Conn, error) {
 		if err != nil {
 			return nil, fmt.Errorf("imap connect plain: %w", err)
 		}
-		c, err := imapclient.New(raw, nil)
-		if err != nil {
-			raw.Close()
-			return nil, fmt.Errorf("imap client plain: %w", err)
-		}
+		c := imapclient.New(raw, nil)
 		return &Conn{Client: c, raw: raw}, nil
 
 	default: