Reduce KPI font size on small screens to prevent overlapping of large
numbers while preserving the desktop layout.
Changes:
- InvitationCard.jsx: use `text-base sm:text-2xl` for
pending earnings, total earnings, and invite count.
- RechargeCard.jsx: use `text-base sm:text-2xl` for
current balance, historical usage, and request count.
Impact:
- Visual-only; no behavioral changes.
- Desktop/tablet unchanged.
- Lint passes.
Files:
- web/src/components/topup/InvitationCard.jsx
- web/src/components/topup/RechargeCard.jsx
