Implement Login Page, Add App Initialization, Router, and Theme Management

finlog_app/app/lib/features/login/pages/login_page.dart

@@ -0,0 +1,82 @@
+import 'package:app/app/router.dart';
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+
+class LoginPage extends StatefulWidget {
+  const LoginPage({super.key});
+
+  @override
+  State<LoginPage> createState() => _LoginPageState();
+}
+
+class _LoginPageState extends State<LoginPage> {
+  bool _loading = false;
+
+  Future<void> _simulateLogin() async {
+    if (_loading) return;
+    setState(() => _loading = true);
+
+    // Simulate latency, perform demo login, then go home.
+    await Future<void>.delayed(const Duration(milliseconds: 900));
+    // await App.service<Auth>().login('demo', 'demo');
+
+    if (!mounted) return;
+    context.go(AppRoute.home.path);
+
+    setState(() => _loading = false);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return Scaffold(
+      appBar: AppBar(title: const Text('Login')),
+      body: Center(
+        child: ConstrainedBox(
+          constraints: const BoxConstraints(maxWidth: 360),
+          child: Column(
+            mainAxisAlignment: MainAxisAlignment.center,
+            children: [
+              const FlutterLogo(size: 64),
+              const SizedBox(height: 24),
+              Text('Please sign in', style: theme.textTheme.titleMedium),
+              const SizedBox(height: 24),
+              SizedBox(
+                width: double.infinity,
+                child: ElevatedButton(
+                  onPressed: _loading ? null : _simulateLogin,
+                  child: AnimatedSwitcher(
+                    duration: const Duration(milliseconds: 250),
+                    transitionBuilder: (child, anim) =>
+                        FadeTransition(opacity: anim, child: child),
+                    child: _loading
+                        ? const SizedBox(
+                            key: ValueKey('loading'),
+                            width: 20,
+                            height: 20,
+                            child: CircularProgressIndicator(strokeWidth: 2),
+                          )
+                        : const Text('Login', key: ValueKey('text')),
+                  ),
+                ),
+              ),
+              const SizedBox(height: 12),
+              AnimatedSwitcher(
+                duration: const Duration(milliseconds: 250),
+                child: _loading
+                    ? Padding(
+                        padding: const EdgeInsets.only(top: 4),
+                        child: Text(
+                          'Signing you in…',
+                          style: theme.textTheme.bodySmall,
+                        ),
+                      )
+                    : const SizedBox.shrink(),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}