## Description Add Zustand to manage shared frontend state in a more structured way. Use the store for application state that is shared across multiple pages or components, such as authentication state and gallery-related state, while keeping local component state in React where appropriate. ## Done when - [x] Zustand is added to the frontend - [x] Shared authentication state is moved to a Zustand store - [x] Relevant gallery-related shared state is handled through the store where appropriate - [x] Components use the shared store instead of duplicating or manually passing shared state - [x] Existing login, profile and gallery functionality still works as before