Remove Google auth: drop google_sign_in, google-services.json, gradle plugin; keep email+password+fingerprint

lib/auth_screen.dart

@@ -1,5 +1,4 @@
 import 'package:flutter/material.dart';
-import 'package:google_sign_in/google_sign_in.dart';
 import 'package:provider/provider.dart';
 import 'package:login_vault_app/auth_service.dart';
 import 'package:login_vault_app/dashboard_screen.dart';
@@ -83,24 +82,6 @@ class _AuthScreenState extends State<AuthScreen> {
     }
   }
 
-  Future<void> _signInGoogle() async {
-    setState(() => _busy = true);
-    try {
-      final gs = GoogleSignIn(scopes: ['email']);
-      final account = await gs.signIn();
-      if (account?.email != null) {
-        await widget.auth.registerWithGoogle(account!.email);
-        _goToDashboard(account.email);
-      } else {
-        setState(() => _error = 'Google sign-in dibatalkan');
-      }
-    } catch (e) {
-      setState(() => _error = 'Google sign-in gagal: ${e.toString()}');
-    } finally {
-      if (mounted) setState(() => _busy = false);
-    }
-  }
-
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -145,12 +126,6 @@ class _AuthScreenState extends State<AuthScreen> {
                             ? 'Belum punya akun? Daftar'
                             : 'Sudah punya akun? Masuk'),
                       ),
-                      const Divider(),
-                      OutlinedButton.icon(
-                        onPressed: _signInGoogle,
-                        icon: const Icon(Icons.login),
-                        label: const Text('Lanjut dengan Google'),
-                      ),
                     ],
                   ),
           ],