feat(app): implement Product Scan review flow, dynamic batch expiry picker, custom PDFs, PO relationships, and aligned card layouts

backend/sources/product_accuracy_history.jsonl

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+{"timestamp":"2026-07-08T08:39:20.434Z","commit":"9ff4a4a","imageCount":{"training":2,"validation":0},"failedImages":[],"fields":{"training":{"no_sku":{"correct":1,"total":2},"nama_item":{"correct":1,"total":2},"expiry_date":{"correct":2,"total":2}},"validation":{"no_sku":{"correct":0,"total":0},"nama_item":{"correct":0,"total":0},"expiry_date":{"correct":0,"total":0}}}}