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.
Alexander
0ab98690eb
