sequenceDiagram
    autonumber
    participant App as Flutter Mobile App
    participant Cache as Local Storage (FFAppState)
    participant Auth as Supabase Auth (GoTrue)
    participant PostgREST as Supabase PostgREST
    participant OneSignal as OneSignal Flutter SDK

    App->>Cache: Read cached UserProfileStruct & EnrolledCourses
    alt Cache Valid
        App->>App: Render Dashboard UI instantly (0ms)
    else Cache Expired / Empty
        App->>App: Render Skeleton Loader
    end

    App->>Auth: Verify JWT Session
    alt Session Valid
        App->>OneSignal: Initialize SDK & acquire Subscription ID
        OneSignal-->>App: Return Subscription ID
        App->>PostgREST: Call register_device(subscription_id)
        
        App->>PostgREST: Call syncAppData(force: false)
        PostgREST-->>App: Return updated classes, attendance, preferences
        App->>Cache: Update FFAppState & reset TTL timestamps
        App->>App: Re-render UI with latest server state
    else Session Expired
        App->>Auth: Attempt refresh_token exchange
        alt Refresh Failed
            App->>App: Navigate to /login
        end
    end