fix (importer): Renamed root collection for ISL Virtual Exhibitions (#1421)

fix (importer): Renamed root collection for ISL Virtual Exhibitions (#1421)

- **Importer**: renamed the marker collection's title to "Virtual Exhibitions" in [exhibitions-root-collection-importer.ts](scripts/importer/src/importers/phase-01/exhibitions-root-collection-importer.ts), plus consistent updates to the doc comments and log messages in `mwnf3-exhibition-importer.ts` and the CLI pipeline entry name in `cli/import.ts`. Left `internal_name`/`backward_compatibility`/the `key:` pipeline identifier unchanged — those are stable pipeline keys, not display text.
- **Exporter**: confirmed no change needed — it's fully data-driven (reads `title` from `collection_translations` at export time, no hardcoded strings).
- **Database**: ran the SQL update against the **local docker DB only** (port 3316) — confirmed the row changed from "Exhibitions" → "Virtual Exhibitions". OVH was left untouched, since `ship` hasn't run yet.
- Typecheck and lint both clean.

Co-authored-by: Pascal HAVELANGE <havelangep@hotmail.com>