Epic #74.11: SRP refactor desktop-tauri frontend app

[ppotepa]

Parent: #74

Objective

Split hotspot file into smaller modules/components with single-responsibility boundaries.

Target

• File: desktop/apps/desktop-tauri/src/App.tsx
• Stack: TypeScript/Solid
• Current size: ~938 LOC

Scope

• Extract cohesive domains/functions into dedicated files/modules.
• Keep public behavior and contracts stable.
• Reduce file responsibility breadth and coupling.

Definition of Done

• Main hotspot file reduced and responsibilities separated.
• Existing checks/tests/smoke flows remain green.
• No functional regression in runtime behavior.