Add platform-specific UI implementations (Desktop vs Mobile) via abstractions/DI

[bernatvadell]

We need the ability to ship different UI implementations for mobile and desktop (layout, controls, input behavior, UX flow). This should be built on top of the upcoming DI-based service/control resolution so we can swap implementations cleanly per platform.

Goals / Notes:

• Define UI abstraction boundaries (e.g. IUiFactory, IControlFactory, IInputAdapter, IUiTheme, etc.).

• Provide separate implementations for Desktop and Mobile:

  • different layouts / scaling rules
  • touch-first controls (mobile) vs mouse/keyboard-first controls (desktop)
  • platform-specific widgets (TextField, cursor/mouse, virtual keyboard, etc.)

• Register implementations per platform through DI (avoid #if branching scattered across UI code).

• Keep shared UI logic reusable where possible (styles, resources, common control contracts).

[bernatvadell]

Related with #67

[bernatvadell]

We keep this but without the DI layer.