Implement FirebaseAuthView for Google and GitHub Sign-In

This commit adds the `FirebaseAuthView` class, a Flutter widget that serves as the UI for user authentication using Google and GitHub. The class uses the `AuthService` to handle the actual sign-in logic.

Features:
- Added an OutlinedButton for Google Sign-In, styled with Google's colors and logo.
- Added an OutlinedButton for GitHub Sign-In, styled with GitHub's colors and logo.
- Integrated the `AuthService` methods for Google and GitHub sign-in.

frontend/lib/views/auth/firebase_auth_view.dart

@@ -0,0 +1,71 @@
+import 'package:flutter/material.dart';
+import 'package:auto_gpt_flutter_client/services/auth_service.dart';
+
+class FirebaseAuthView extends StatelessWidget {
+  // TODO: This should be initialized in the main.dart instead of here
+  final AuthService _authService = AuthService();
+
+  FirebaseAuthView({super.key}); // Initialize the auth service
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: Center(
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: <Widget>[
+            OutlinedButton(
+              onPressed: () async {
+                final user = await _authService.signInWithGoogle();
+                if (user != null) {
+                  print(
+                      "Successfully signed in with Google: ${user.user?.displayName}");
+                }
+              },
+              style: OutlinedButton.styleFrom(
+                foregroundColor: Colors.blue,
+                side: const BorderSide(color: Colors.blue, width: 2),
+                padding:
+                    const EdgeInsets.symmetric(horizontal: 20, vertical: 20),
+              ),
+              child: Row(
+                mainAxisSize: MainAxisSize.min,
+                children: [
+                  Image.asset('assets/google_logo.svg.png', width: 24),
+                  const SizedBox(width: 8),
+                  const Text('Sign in with Google',
+                      style: TextStyle(fontWeight: FontWeight.w300)),
+                ],
+              ),
+            ),
+            const SizedBox(height: 20),
+            OutlinedButton(
+              onPressed: () async {
+                final user = await _authService.signInWithGitHub();
+                if (user != null) {
+                  print(
+                      "Successfully signed in with GitHub: ${user.user?.displayName}");
+                }
+              },
+              style: OutlinedButton.styleFrom(
+                foregroundColor: Colors.black,
+                side: const BorderSide(color: Colors.black, width: 2),
+                padding:
+                    const EdgeInsets.symmetric(horizontal: 20, vertical: 20),
+              ),
+              child: Row(
+                mainAxisSize: MainAxisSize.min,
+                children: [
+                  Image.asset('assets/github_logo.svg.png', width: 24),
+                  const SizedBox(width: 8),
+                  const Text('Sign in with GitHub',
+                      style: TextStyle(fontWeight: FontWeight.w300)),
+                ],
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}