Improve cookies & lint various files

src/lib/components/NavBar.svelte

src/lib/components/tutorial/BudgetButtonModal.svelte

src/lib/components/tutorial/StartTutorial.svelte

src/lib/server/user_handler.ts

src/routes/+page.svelte

src/routes/auth/login/+server.ts

src/routes/auth/login_callback/+server.ts

src/routes/auth/logout/+server.ts