inventory: barcode scanner in Add-item dialog

Add a camera barcode/QR scanner (components/scan/barcode-scanner.tsx,
@zxing/browser lazy-loaded) and a Barcode/NDC field to the pharmacy
Add-item dialog. Scanning a GS1 DataMatrix auto-fills expiry (AI 17) and
lot (AI 10 -> notes), with the GTIN (AI 01) as the barcode; plain 1D
barcodes drop straight into the field. Persists a nullable inventory
barcode column (migration 0036) through the type/validation/service, and
surfaces it on the item detail. i18n added to all locales.

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

backend/src/services/inventory.ts

@@ -21,6 +21,7 @@ function toInventoryItem(row: InventoryRow): InventoryItem {
     stockQuantity: row.stockQuantity,
     reorderThreshold: row.reorderThreshold,
     location: row.location,
+    barcode: row.barcode,
     expiresAt: row.expiresAt,
     notes: row.notes,
     createdAt: row.createdAt.toISOString(),
@@ -38,6 +39,7 @@ function columns(orgId: string, input: InventoryInput, createdBy?: string) {
     stockQuantity: input.stockQuantity,
     reorderThreshold: input.reorderThreshold,
     location: input.location,
+    barcode: input.barcode ?? null,
     expiresAt: input.expiresAt ?? null,
     notes: input.notes ?? null,
     ...(createdBy ? { createdBy } : {}),