Introduce redesigned UI elements for the new design system:
- **CommentsPanel** – displays agent‑driven edits with diff view, batch actions, and filtering.
- **PageHistoryModal** – full‑screen modal for browsing page revisions, includes a mini‑calendar and version rendering.
- **TimeWorkedModal** – visualizes work and agent sessions per day with grid or phase axes.
These components replace legacy panels, use Mantine v7, support dark/light themes, and provide richer interactions.
