feat(shopping): loyalty-card modal with build-time barcodes

Adds a CreditCard button on the shopping list that opens a modal
showing the user's Coop Supercard (Data Matrix) and Migros Cumulus
(Code 128). Card numbers come from SHOPPING_COOP_SUPERCARD_NUMBER
and SHOPPING_MIGROS_CUMULUS_NUMBER env vars; a prebuild script
renders each to an SVG (~1-2 kB) in static/shopping/ so no barcode
library ships to the client. Cards missing their env var are
silently skipped, and the generated SVGs are gitignored to keep
personal numbers out of the repo.

package.json

@@ -1,11 +1,11 @@
 {
 	"name": "homepage",
-	"version": "1.46.28",
+	"version": "1.47.0",
 	"private": true,
 	"type": "module",
 	"scripts": {
 		"dev": "vite dev",
-		"prebuild": "bash scripts/subset-emoji-font.sh && pnpm exec vite-node scripts/generate-mystery-verses.ts && pnpm exec vite-node scripts/download-models.ts",
+		"prebuild": "bash scripts/subset-emoji-font.sh && pnpm exec vite-node scripts/generate-mystery-verses.ts && pnpm exec vite-node scripts/download-models.ts && pnpm exec vite-node scripts/generate-loyalty-cards.ts",
 		"build": "vite build",
 		"preview": "vite preview",
 		"check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
@@ -37,6 +37,7 @@
 		"@types/node": "^22.12.0",
 		"@types/node-cron": "^3.0.11",
 		"@vitest/ui": "^4.1.2",
+		"bwip-js": "^4.10.1",
 		"jsdom": "^27.2.0",
 		"svelte": "^5.55.1",
 		"svelte-check": "^4.4.6",