fix(desktop): improve small-screen navigation layout

[Grace256c]

What & Why

Fixes the ODE Desktop layout on small and low-resolution windows.

At widths of 1080px and below, the existing vertical sidebar is reorganized into a compact horizontal header so navigation no longer consumes most of the viewport. This keeps the active page immediately visible while preserving access to Data and Workbench navigation, the application mode switch, and server status.

The existing wide-screen sidebar layout remains unchanged.

Closes #958

Type of Change

• Bug fix
• New feature / enhancement
• Refactor / cleanup
• Documentation
• Chore / other

Component(s) Changed

• formulus (React Native mobile app)
• formulus-formplayer (form WebView UI)
• synkronus (Go backend)
• synkronus-cli (command-line client)
• synkronus-portal (web admin UI)
• desktop (Tauri app)
• packages (tokens / components)
• Documentation / DevOps / CI

Testing

• Added/updated tests
• Manually tested
• Not applicable

Manual verification was performed at ODE Desktop's configured minimum window size of 960 × 640.

Verified:

• All Data destinations remain accessible: Profiles, Observations, Import, Export, Sync, and About.
• All Workbench destinations remain accessible: Bundles, Form preview, and Custom app.
• Active navigation state remains visible.
• Data / Workbench switching remains functional.
• Page content remains visible below the compact navigation.
• The normal wide-screen sidebar layout remains unchanged.

Automated checks:

• pnpm run format:check — passed
• pnpm run lint — 0 errors; 2 pre-existing unrelated warnings
• pnpm test — 155/155 tests passed
• pnpm typecheck — passed
• git diff --check — passed

Checklist

• Pre-flight checks for changed packages passed (lint / format / tests)
• Breaking changes (if any) have migration steps
• Related issue linked with Closes #958

[najuna-brian]

Thanks @Grace256c Approving!

Nit (optional): could you drop the CSS comment above .sidebar?