## Context
SSE metadata events for overridable entities (viewField, viewFieldGroup,
pageLayoutWidget, pageLayoutTab) were sending raw flat entity data
without resolving overrides into base properties or filtering isActive:
false entities. This caused the frontend to display stale/incorrect
values (e.g., a hidden viewField still appearing visible).
## Implementation
Add a sanitization step in
MetadataEventPublisher.enrichMetadataEventBatch that resolves overrides
and converts isActive transitions into the appropriate event types
(deactivated -> delete, reactivated -> create), matching what GraphQL
resolvers already do
