fix(auth): 登录页靠上排列并支持外部失焦

test/auth/auth_landing_test.dart

@@ -52,6 +52,10 @@ void main() {
     expect(find.byKey(const Key('auth-entry-phone')), findsOneWidget);
     expect(find.byKey(const Key('auth-entry-email')), findsOneWidget);
     expect(find.byKey(const Key('auth-legal')), findsOneWidget);
+    expect(
+      tester.getTopLeft(find.byKey(const Key('auth-landing'))).dy,
+      lessThan(80),
+    );
 
     await tester.tap(find.byKey(const Key('auth-entry-phone')));
     await tester.pumpAndSettle();