fix(welcome, components): disable guide cues in the app until welcome modal is hidden

[gribnoysup]

Spotted this issue while debugging an e2e test flake: on a fresh compass install guide cues are awkwardly disaplyed over the welcome modal. Interacting with the modal dismisses both, so you don't know anymore where it was pointing. This patch addresses the issue by disabling guide cues in the app completely until welcome modal is hidden.

Before	After
Kapture.2025-10-31.at.18.38.41.mp4	Kapture.2025-10-31.at.18.28.44.mp4

The gist of the changes in this patch:

• Change the logic around showedNetworkOptIn: only set it to true after the modal is closed.
  • Refactor WelcomeModal into a plugin so that all this logic of changing the preference on close can be encapsulated in a single place
  • As a related drive-by: remove ensureDefaultConfigurableUserPreferences from preferences interface and implementation, I couldn't see any reason to have this logic in compass, it just immediately sets some values to slightly different defaults on app start
• Change GuideCue component to disable itself only visually, but keep the state around so that when re-enabled the items will show up on the screen

[ivandevp]

LGTM