settings: clear Android bottom inset so last button is not clipped

Append ui.add_space(View::get_bottom_inset()) at the end of
SettingsContent::ui. The settings screen supplies no bottom inset (its
tab panel is hidden and the CentralPanel frame uses bottom:0), so the
final FADERS Settings button clipped under 3-button nav / the gesture
pill. get_bottom_inset() is 0 off Android, so desktop is unaffected.

src/gui/views/settings/content.rs

@@ -108,5 +108,9 @@ impl SettingsContent {
 			}
 		});
 		ui.add_space(8.0);
+
+		// Clear the Android navigation/gesture bar so the last button is not
+		// clipped or overlaid by the gesture pill. Zero on desktop.
+		ui.add_space(View::get_bottom_inset());
 	}
 }