Fixed card page

[Lucretiel]

Description

This PR fixes the way that the Card page and Cards service load card data, making more use of computed signals instead of manual state sync to make this data available. The overall effect is to fix the bug where the app often navigates away from /card/CARD-ID to / the first time you load it, especially in mobile browsers.

Reattempt of #156

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have run tests (npm run test & npm run e2e) that prove my fix is effective or that my feature works

[Lucretiel]

Done. @seiyria the answer was straightforwardly to make the "flip card" button route to /card/<flippedId>