[Test] Build Delivery Brief route with checkpoint summaries

[iamasx]

Summary

Build a delivery-brief route that shows milestone summaries, shipment checkpoints, and a compact follow-up notes rail.

Scope

• Add a new delivery-brief route.
• Create mock milestone, checkpoint, and follow-up-note data.
• Build milestone summaries, checkpoint cards, and a notes rail.

Acceptance Criteria

• The route displays delivery and checkpoint content clearly.
• Follow-up notes are visible.
• The layout works on narrow and wide screens.
• Tests cover the key render paths.

[iamasx]

Implementation plan:

• Add the delivery-brief route shell and route-specific mock data.
• Build milestone-summary, checkpoint-card, and notes-rail components.
• Compose the page with a delivery-focused layout and responsive behavior.
• Add styling polish and route-level tests.
• Run the standard local checks before finishing.