## Summary
Removes the application **custom settings tab** feature. This is one
half of #22059, split out so it can be reviewed/merged independently
from the variable-types enrichment.
## Changes
- Remove the `SettingsApplicationCustomTab` component and its tab
entry/rendering in `SettingsApplicationDetails`.
- Stop syncing `settingsCustomTabFrontComponent` from application
manifests — `ApplicationManifestMigrationService` now only syncs the
default role.
- Deprecate the now-unused fields (kept for backward compatibility, no
longer read or synced):
- `ApplicationDTO.settingsCustomTabFrontComponentId` (GraphQL
`@deprecated`)
-
`ApplicationManifest.settingsCustomTabFrontComponentUniversalIdentifier`
- the `settingsCustomTabFrontComponentId` column comment on
`ApplicationEntity`
The DB column is intentionally **not dropped**, so existing
installations upgrade cleanly.
martmull
a20ebfa880