Upgrade Svelte to v5 (and SvelteKit to latest v2) #589
Description
Related issues:
Problem statement
TODO
Background
TODO
Mocks
N/A
Acceptance criteria
TODO
Technical implementation details
As part of the upgrade, we should be able to migrate from $app/stores to $app/state automatically using npx sv migrate app-state. See the relevant section of the SvelteKit 2 migration guide for more details.