* core, ui: persist "Remove link tracking" setting on database import
The privacySanitizeLinks preference was stored locally only and absent from
the AppSettings round-trip, so it was lost when migrating to another device
or after a fresh install + DB import. Add the field to the Haskell, Kotlin,
and Swift AppSettings payloads and wire it through iOS group defaults.
* plans: justify privacySanitizeLinks AppSettings round-trip fix