refactor(home): update sellableData state to use array type
fix(account): improve type safety for user data fetching
fix(cart): streamline item removal and purchase handling
fix(cart): ensure cart item updates and deletions are based on cartId and itemId
feat(buy): implement balance checks and updates during purchase process
fix(sellable): ensure cart items are deleted when a sellable is removed
feat(user): add conflict checks for shop creation to prevent ID collisions
