fix(nav,favoritos): unclip the overflow menu and smooth the tab transition

Two user-reported bugs from on-device testing.

The favourites overflow menu carried `constraints: tightFor(38x42)`,
which sizes the POPUP rather than the button -- every item was clipped to
its first letter, so users saw "M" and "E" instead of the labels. The
existing test passed throughout because find.text matches a Text widget
whether or not it is visually clipped; the new guard measures the laid-out
width instead.

The bottom bar's ink splash had no shape, painting a hard square over the
icon, and the active tab's lift, dim, icon size and label all changed
instantly while the balloon slid -- the balloon glided and its contents
teleported. All four now share the balloon's duration and curve.

lib/pantallas/pantalla_favoritos.dart

@@ -465,7 +465,13 @@ class _FilaFavorito extends StatelessWidget {
               context,
             ).colorScheme.onSurface.withValues(alpha: 0.45),
           ),
-          constraints: const BoxConstraints.tightFor(width: 38, height: 42),
+          // NO `constraints:` here. That property sizes the POPUP MENU, not
+          // the button — a tightFor(38x42) clipped every menu item down to
+          // its first letter ("M" for "Mover a lista", "E" for "Eliminar de
+          // favoritos"), which is what users actually saw. Constrain the
+          // tap target instead.
+          padding: EdgeInsets.zero,
+          iconSize: 20,
           onSelected: (accion) {
             if (accion == 'assign') _asignar(context);
             if (accion == 'remove') _eliminar(context);