[Test] Add Forecast Desk route with trend snapshots

[iamasx]

Summary

Add a forecast-desk route that presents trend snapshots, short forecast notes, and a compact metric comparison band.

Scope

• Add a dedicated forecast-desk route.
• Create mock forecast, trend, and comparison data.
• Build snapshot cards, notes sections, and a comparison band.
• Aim for roughly 400-500 changed lines overall, staying reasonably close to that range.

Acceptance Criteria

• The route renders forecast and trend content clearly.
• Comparison information is visible.
• The layout remains readable across breakpoints.
• Tests cover the main route content.
• Final PR diff is roughly 400-500 changed lines.

[iamasx]

Implementation plan:

• Add the forecast-desk route shell and supporting mock data.
• Build trend snapshot, forecast notes, and comparison components.
• Compose the route with a concise forecast-oriented layout and responsive structure.
• Add styling refinements and route-level tests.
• Run local checks and keep the final diff near the 400-500 line target.