feat(import): data model for the bulk CSV/XLSX importer

First increment of the importer (docs/superpowers/specs/2026-06-01-bulk-import-design.md):
the three port-scoped tables, no changes to entity tables.

- import_batches — one row per run: entity_type, filename, storage_key,
  status, conflict_policy, mapping_json, live counts, created_by, timestamps.
- import_batch_rows — per-row action ledger (inserted/updated/skipped/errored)
  with entity_id + error; partial index on inserted rows powers Undo.
- import_mappings — saved column mappings, unique per (port, entity, name).

Migration 0090 applied via psql; schema re-exported from the index.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lib/db/schema/index.ts

@@ -65,6 +65,9 @@ export * from './gdpr';
 // Migration ledger (one-shot scripts - NocoDB import etc.)
 export * from './migration';
 
+// Bulk CSV/XLSX importer (batches, per-row ledger, saved mappings)
+export * from './imports';
+
 // Website submissions (dual-write capture from the marketing site)
 export * from './website-submissions';