[Conflict Test] Reserve Grid shared route-entry overlap

[iamasx]

Summary

Build a reserve-grid route with shared route-entry overlap so it intentionally edits common homepage and app-shell files.

Conflict Surface

• src/app/reserve-grid/page.tsx
• src/app/page.tsx
• src/app/layout.tsx
• src/app/globals.css

Scope

• Add or refine the reserve-grid route.
• Update shared entry points and global presentation.
• Aim for roughly 400-500 changed lines overall, staying reasonably close to that range.

Acceptance Criteria

• The route exists and is linked from the landing page.
• Shared layout or global style changes are included.
• The work intentionally overlaps common files to create merge conflicts after one PR lands.
• Final PR diff is roughly 400-500 changed lines.

[iamasx]

Implementation plan:

• Add the reserve-grid route shell and supporting mock data.
• Build route-specific reservation and summary components.
• Update shared files such as src/app/page.tsx, src/app/layout.tsx, and src/app/globals.css so the issue intentionally overlaps common surfaces.
• Add styling refinements and representative route tests.
• Run local checks and keep the final diff near the 400-500 line target.