SwiftUI view refactor

• Default to vanilla SwiftUI: local state in the view, shared dependencies in the environment, business logic in services or models. Add a view model only if one exists or is requested.
• Extract dedicated View types for non-trivial sections. Keep computed some View helpers rare and small.
• Keep a stable view tree. Put conditions inside sections and modifiers, not as if/else root swaps.
• Keep business logic out of body, .task, .onAppear, .onChange, and .refreshable. Call small private methods.
• Pass observables explicitly. Avoid bootstrapIfNeeded-style delayed setup.