feat: same-host SSH optimization (Exec cp/mv), per-file progress for all remote copies

- SSHClient.Exec() and ExecWithProgress() for server-side commands
- SSHHost.SameAs() and SSHClient.SameHostAs() for host comparison
- Same-host copy uses ExecWithProgress('cp -rv') with per-line progress
- Same-host move uses Exec('mv'), instant server-side rename
- CopyDirFromRemote/ToRemote/BetweenRemotes with per-file progress callbacks
- Context cancellation support for all remote copy operations
- Two-phase remote copy: count files first, then transfer with progress bar
- Fix: consistent modal colors (Enter=Accent, Cancel=CancelButton, Background=Accent)

internal/fs/remote/host.go

@@ -51,6 +51,12 @@ func (h SSHHost) Addr() string {
 	return h.HostName + ":" + h.Port
 }
 
+// SameAs returns true if two hosts point to the same server.
+func (h SSHHost) SameAs(other SSHHost) bool {
+	return h.HostName == other.HostName &&
+		(h.Port == other.Port || (h.Port == "" && other.Port == "22") || (h.Port == "22" && other.Port == ""))
+}
+
 // HostStore manages SSH hosts from both ~/.ssh/config and user-added hosts.
 type HostStore struct {
 	customHosts []SSHHost