feat: add Flutter schema-driven form cards

mobile/lib/app/app.dart

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+import 'package:aioa_mobile/app/router.dart';
+import 'package:aioa_mobile/app/theme.dart';
+import 'package:flutter/material.dart';
+
+class AioaApp extends StatelessWidget {
+  const AioaApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp.router(
+      title: 'AIOA',
+      debugShowCheckedModeBanner: false,
+      theme: buildAioaTheme(),
+      routerConfig: appRouter,
+    );
+  }
+}

mobile/lib/app/router.dart

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+import 'package:aioa_mobile/app/shell.dart';
+import 'package:aioa_mobile/features/assistant/presentation/assistant_page.dart';
+import 'package:aioa_mobile/features/form/presentation/leave_form_page.dart';
+import 'package:aioa_mobile/features/profile/presentation/profile_page.dart';
+import 'package:aioa_mobile/features/tasks/presentation/tasks_page.dart';
+import 'package:aioa_mobile/features/workspace/presentation/workspace_page.dart';
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+
+final appRouter = GoRouter(
+  initialLocation: '/workspace',
+  routes: [
+    ShellRoute(
+      builder: (context, state, child) =>
+          AioaShell(location: state.uri.path, child: child),
+      routes: [
+        GoRoute(path: '/workspace', builder: (_, _) => const WorkspacePage()),
+        GoRoute(path: '/assistant', builder: (_, _) => const AssistantPage()),
+        GoRoute(path: '/tasks', builder: (_, _) => const TasksPage()),
+        GoRoute(path: '/profile', builder: (_, _) => const ProfilePage()),
+      ],
+    ),
+    GoRoute(
+      path: '/leave/new',
+      pageBuilder: (context, state) => MaterialPage<void>(
+        fullscreenDialog: true,
+        child: const LeaveFormPage(),
+      ),
+    ),
+  ],
+);

mobile/lib/app/shell.dart

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+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+
+class AioaShell extends StatelessWidget {
+  const AioaShell({super.key, required this.location, required this.child});
+
+  final String location;
+  final Widget child;
+
+  @override
+  Widget build(BuildContext context) {
+    final index = switch (location) {
+      String path when path.startsWith('/assistant') => 1,
+      String path when path.startsWith('/tasks') => 2,
+      String path when path.startsWith('/profile') => 3,
+      _ => 0,
+    };
+    return Scaffold(
+      body: SafeArea(child: child),
+      bottomNavigationBar: NavigationBar(
+        selectedIndex: index,
+        onDestinationSelected: (value) {
+          const paths = ['/workspace', '/assistant', '/tasks', '/profile'];
+          context.go(paths[value]);
+        },
+        destinations: const [
+          NavigationDestination(
+            icon: Icon(Icons.grid_view_rounded),
+            label: '工作台',
+          ),
+          NavigationDestination(
+            icon: Icon(Icons.auto_awesome_rounded),
+            label: 'AI 助手',
+          ),
+          NavigationDestination(
+            icon: Icon(Icons.task_alt_rounded),
+            label: '待办',
+          ),
+          NavigationDestination(
+            icon: Icon(Icons.person_outline_rounded),
+            label: '我的',
+          ),
+        ],
+      ),
+    );
+  }
+}

mobile/lib/app/theme.dart

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+import 'package:flutter/material.dart';
+
+ThemeData buildAioaTheme() {
+  const seed = Color(0xFF3157D5);
+  final scheme = ColorScheme.fromSeed(
+    seedColor: seed,
+    brightness: Brightness.light,
+    surface: const Color(0xFFF7F8FC),
+  );
+  return ThemeData(
+    colorScheme: scheme,
+    useMaterial3: true,
+    scaffoldBackgroundColor: scheme.surface,
+    cardTheme: const CardThemeData(
+      elevation: 0,
+      margin: EdgeInsets.zero,
+      shape: RoundedRectangleBorder(
+        borderRadius: BorderRadius.all(Radius.circular(20)),
+        side: BorderSide(color: Color(0xFFE6E8F0)),
+      ),
+    ),
+    inputDecorationTheme: const InputDecorationTheme(
+      filled: true,
+      fillColor: Colors.white,
+      border: OutlineInputBorder(
+        borderRadius: BorderRadius.all(Radius.circular(14)),
+        borderSide: BorderSide(color: Color(0xFFDDE1EA)),
+      ),
+      enabledBorder: OutlineInputBorder(
+        borderRadius: BorderRadius.all(Radius.circular(14)),
+        borderSide: BorderSide(color: Color(0xFFDDE1EA)),
+      ),
+      contentPadding: EdgeInsets.symmetric(horizontal: 16, vertical: 14),
+    ),
+  );
+}