Flutter UI Implementation

Implement the approved experience inside the host project's conventions.

Before Editing

1. Confirm the visual direction, behavior, state matrix, and acceptance criteria. If absent and choices are material, return to $flutter-design.
2. Inspect neighboring screens, theme, routing, state management, generated code rules, test style, and current worktree changes.
3. Read only the relevant references: references/flutter-architecture.md, references/adaptive-layouts.md, references/navigation-and-input.md, and references/states-and-feedback.md. Read references/connected-product-workflows.md when one surface combines multiple domains or data sources.

Implement