Add state management templates

[ssestak]

Summary

Extends the SwiftUI App Xcode template with a reusable state-management layer (loading / empty / error / ready) and adds a new Projection Scene variant to the Scene template. Existing example files are updated to demonstrate the cache-projection pattern end-to-end. Also adds a build-time warning to remind developers to set UILaunchScreen in Info.plist.

Architecture

flowchart LR
    subgraph Model["Model layer (new)"]
        CS[ComponentState]
        IS[ItemState]
        AS[ArrayState]
        SIC[StateInfoConfig]
        CP[CacheProjection]
        MK[Mockable]
    end

    subgraph Views["UI layer (new)"]
        SIV[StateInfoView]
        CSV[ComponentStateView]
        ISV[ItemStateView]
    end

    subgraph Scene["Example scene (updated)"]
        ECM[ExampleComponentModel]
        ECP[ExampleCacheProjection]
        EC[ExampleComponent]
    end

    DC[(DataCache<DataCacheModel>)] --> ECM
    ECM -->|projection| ECP
    ECP -->|state| CS
    EC -->|wraps content| CSV
    CSV --> CS
    CSV -.uses.-> SIV
    ISV --> IS
    SIV --> SIC

    CS -.config.-> SIC
    IS -.config.-> SIC
    AS -.config.-> SIC
    ECP -.conforms.-> CP

Loading

Key Changes

• SwiftUI App template — adds ComponentState, ItemState, ArrayState enums for screen / item / collection lifecycle, plus StateInfoConfig and a unified StateInfoView for empty/error presentation. ComponentStateView and ItemStateView wrap content and switch on state.
• CacheProjection pattern — generic CacheProjection protocol with concrete ExampleCacheProjection; the example ComponentModel exposes a computed projection property that reads dataCache.value, so @Observable re-renders the view on cache changes (no Combine).
• Scene template — new Projection Scene variant generates Component, ComponentModel, and CacheProjection together; adds a projectionName template option.
• Swift 6 concurrency — state and data model types marked nonisolated so they can be used from any actor context.
• App template warning — emits a #warning to add UILaunchScreen to Info.plist, preventing the legacy compatibility-mode pitfall on modern devices.

Test Plan

• Generate a new project from the SwiftUI App template and verify it builds
• Create a Projection Scene via the new template variant and verify file layout / naming
• Confirm ComponentStateView renders loading / empty / error / ready states correctly in previews

[jmarek41]

Krása 👏. Jen pokud bychom přidali i ten SwiftFormat tak to chce čeknout že nebude nic měnit v těchto filech po prvním spuštění ať je to čistota. Myslím v těch vygenerovaných filech.