feat(planning): Add TaskReview component for task approval workflow (#214)

* feat(planning): Add TaskReview component for task approval workflow

Implements hierarchical tree view component for reviewing and approving
task breakdown during planning phase. Users can select/deselect individual
tasks or entire issues before approving to start development.

Key features:
- Sprint-level grouping with expand/collapse
- Issue-level checkboxes with indeterminate state
- Task-level selection with descriptions
- Dynamic summary showing selected task count
- Approval API integration with loading/error states
- Navigation to dashboard on successful approval
- Full accessibility support (ARIA, keyboard navigation)

Includes 41 comprehensive tests covering rendering, selection logic,
approval flow, accessibility, and edge cases.

Part of issue 016-3: Task Review Component

* fix(planning): Fix stale closure in toggleIssueTasks callback

Move allSelected computation inside the functional state updater
to use the latest prev Set instead of capturing selectedTaskIds
from the outer closure, which could be stale.

Author: frankbria