Fix shop: Surge refresh should not resurrect purchased card offers

[endrawes0]

Fixes #129.

Root cause:

• Purchasing a shop card only removed the UI button; the card id stayed in ShopManager.card_offers.
• Buying Surge triggers a shop UI refresh, which rebuilds from card_offers, so previously purchased cards can reappear.

Change:

• On card purchase, remove that card id from ShopManager.card_offers so future refreshes reflect current offers.

Test plan:

• Enter shop, buy any card, then buy Surge.
• Confirm the purchased card does not reappear in the shop offers.

Closes #129.