fix(tui): default SMTP port to 465 in the account form

NewAccountForm prefilled defaults for mode, IMAP port, and both securities but
left SMTP port blank. Default it to 465 to match `account add --smtp-port`.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/tui/account.go

@@ -203,6 +203,9 @@ func NewAccountForm(initial Fields, editing bool) AccountForm {
 	if initial.IMAPSecurity == "" {
 		initial.IMAPSecurity = "tls"
 	}
+	if initial.SMTPPort == "" {
+		initial.SMTPPort = "465"
+	}
 	if initial.SMTPSecurity == "" {
 		initial.SMTPSecurity = "tls"
 	}

internal/tui/account_test.go

@@ -111,6 +111,17 @@ func TestFieldsFromAccountRoundTrip(t *testing.T) {
 	}
 }
 
+func TestNewAccountFormDefaultsSMTPPort(t *testing.T) {
+	f := NewAccountForm(Fields{}, false).collect()
+	if f.SMTPPort != "465" {
+		t.Fatalf("SMTP port should default to 465, got %q", f.SMTPPort)
+	}
+	// The other prefilled defaults must remain intact.
+	if f.IMAPPort != "993" || f.Mode != "RO" || f.IMAPSecurity != "tls" || f.SMTPSecurity != "tls" {
+		t.Fatalf("existing defaults regressed: %+v", f)
+	}
+}
+
 func TestAccountFormSubmitValid(t *testing.T) {
 	m := NewAccountForm(validFields(), false)
 	// Enter submits; with valid fields the form completes.