Add bulk CSV product import for POS (retail + restaurant)

Customers with large catalogs can upload a CSV instead of adding products one by
one. Mode-aware: restaurant imports into the local catalog (chunked INSERT,
categories resolved/created by name); retail batches to the CRM products/bulk
endpoint. Streamed parsing + batched writes handle thousands of rows in one
request. Includes a downloadable template, an Import button on both product
pages, and a skipped-rows report.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

storage/framework/testing/events-import.json

@@ -0,0 +1 @@
+{"qr_wallets":[],"qr_codes":[{"platform_id":10,"owner_public_id":"usr_events_owner","owner_email":"dejah85@example.org","short_code":"demo-programme","type":"itinerary","label":"Demo Programme","payload":"{\"content\":{\"title\":\"Demo Programme\"},\"style\":[]}","is_active":true,"scans_total":0,"created_at":"2026-06-24 00:00:25","updated_at":"2026-06-24 00:00:25","destination_updated_at":"2026-06-24 00:00:25"},{"platform_id":11,"owner_public_id":"usr_events_owner","owner_email":"dejah85@example.org","short_code":"demo-event","type":"event","label":"Demo Event","payload":"{\"content\":{\"name\":\"Demo Event\",\"programme_qr_id\":10},\"style\":[]}","is_active":true,"scans_total":0,"created_at":"2026-06-24 00:00:25","updated_at":"2026-06-24 00:00:25","destination_updated_at":"2026-06-24 00:00:25"}],"qr_event_registrations":[],"qr_scan_events":[],"qr_transactions":[]}