Remove the object-metadata-repository injection layer (#24801)

## What

The last legacy data-access layer: `object-metadata-repository` was the
pre-v1 repository injection system
(`ObjectMetadataRepositoryModule.forFeature`,
`@InjectObjectMetadataRepository`, and the metadata-to-repository
mapping). It was down to providing exactly two classes,
`BlocklistRepository` and `TimelineActivityRepository`, and both already
run entirely on `WorkspaceOrmManager` internally, so the layer was pure
dependency-injection ceremony.

- The two repositories become plain providers of the feature modules
that use them (blocklist validation, calendar import, the three
messaging drivers, timeline), injected directly by class.
- `src/engine/object-metadata-repository/` is deleted.
- `WorkspaceSchemaService.executeRawQuery` goes with it: it has been a
throw-only stub ("method not allowed as permissions are not handled at
datasource level") with zero callers, kept alive only by this layer's
era. The schema service keeps its real job, creating and deleting
workspace schemas.

With this, workspace data access has exactly one entry point: the
workspace ORM manager.

## Verification

- `tsgo --noEmit` clean, `oxlint --type-aware` and `oxfmt --check src/`
clean
- Blocklist, timeline, calendar-import, messaging-import and
schema-service suites pass (70 suites, 340 tests)
- Grep gate: no reference to the subsystem remains
- No committed upgrade command is touched


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