Remove idle connection timeout handling

Remove error handling for closed connections

Add progress watchdog to detect stalled accounts

Improve error modal styling and pagination

internal/imapx/copy.go

@@ -3,8 +3,11 @@ package imapx
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"io"
+	"net"
+	"strings"
 	"time"
 
 	"github.com/emersion/go-imap/v2"
@@ -180,6 +183,12 @@ func CopyFolder(ctx context.Context, src, dst *imapclient.Client, srcFolder, dst
 		if err := streamOne(src, dst, dstFolder, q.uid, q.flags, q.internalDate); err != nil {
 			res.Errors++
 			reportErr(msgRef(q.uid, q.subject), "copy message: "+err.Error())
+			// A closed/broken connection won't recover: every remaining APPEND
+			// would fail identically. Abort the folder instead of logging
+			// thousands of the same error; a re-run resumes via dedup.
+			if errors.Is(err, net.ErrClosed) || strings.Contains(err.Error(), "use of closed network connection") {
+				return res, fmt.Errorf("dst connection lost in %q: %w", dstFolder, err)
+			}
 			continue
 		}
 		if err := deps.MarkMigrated(dstFolder, q.key); err != nil {