feat(ui): About in drawer; higher-contrast app icon & splash

Add an "About" entry to the navigation drawer (below Settings) so the
About screen is reachable without opening Settings first.

Recolour the launcher icon and native splash to a white sprout on brand
green (#2F7D34) — the previous dark-green-on-light-green had almost no
contrast. Regenerate Android, iOS and web icons and the light/dark splash.

apps/app_seeds/lib/ui/app_drawer.dart

@@ -55,6 +55,14 @@ class AppDrawer extends StatelessWidget {
                 context.push('/settings');
               },
             ),
+            _DrawerItem(
+              icon: const Icon(Icons.info_outline),
+              label: t.about.title,
+              onTap: () {
+                Navigator.of(context).pop();
+                context.push('/about');
+              },
+            ),
           ],
         ),
       ),