Flutter Idiomatic Flutter

Split the large `build` method by visual responsibility, not into `_buildXxx()` helper methods. Extract each meaningful section into a small `StatelessWidget`, pass only the data and callbacks it needs, and make widgets `const` where possible. This flattens nesting, makes rebuild boundaries clearer, and makes sections independently testable.

```dart
class AccountPage extends StatelessWidget {
  const AccountPage({super.key, required this.account, required this.onSave});

  final Account account;
  final VoidCallback onSave;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Account')),
      body: ListView(
        padding: const EdgeInsets.all(16),
        children: [
          AccountHeader(account: account),
          const Gap(24),
          AccountDetails(account: account),
          const Gap(24),
          SaveAccountButton(onPressed: onSave),
        ],
      ),
    );
  }
}

class AccountHeader extends StatelessWidget {
  const AccountHeader({super.key, required this.account});

  final Account account;

  @override
  Widget build(BuildContext context) {
    final colors = Theme.of(context).colorScheme;
    return ColoredBox(
      color: colors.surfaceContainerHighest,
      child: Padding(
        padding: const EdgeInsets.all(16),
        child: Text(account.name),
      ),
    );
  }
}
```

Prefer `ColoredBox`, `DecoratedBox`, and `Padding` over a catch-all `Container` when each widget has a single purpose. Keep layout widgets shallow; use `const SizedBox.shrink()` for an empty branch. If state becomes substantial, have the page select state from BLoC/Riverpod and pass plain values to these presentation widgets rather than accessing controllers directly in the widget tree.