feat(gui): TOTP tab with QR code modal + revoke (feature-gated)

gui/src/main.rs

@@ -10,6 +10,8 @@ mod keys_page;
 mod policy_form;
 mod policy_page;
 mod recovery_page;
+#[cfg(feature = "totp")]
+mod totp_page;
 
 const APP_ID: &str = "io.dangerousthings.AuthForge";
 
@@ -68,6 +70,12 @@ fn main() -> glib::ExitCode {
         let recovery = recovery_page::RecoveryPage::new(ctx.clone());
         stack.add_titled(&recovery.root, Some("recovery"), "Recovery");
 
+        #[cfg(feature = "totp")]
+        {
+            let totp = totp_page::TotpPage::new(ctx.clone());
+            stack.add_titled(&totp.root, Some("totp"), "TOTP");
+        }
+
         // ToolbarView is libadwaita v1_4-gated; the project sticks with the
         // simpler Box layout for portability (see commit c6a5e94).
         let layout = gtk::Box::new(gtk::Orientation::Vertical, 0);