feat: remove FPX, add UK charity persona features

- Remove FPX payment rail entirely (Malaysian, not UK)
- Add volunteer portal (/v/[code]) with live pledge tracking
- Add public event page (/e/[slug]) with progress bar + social proof
- Add fundraiser leaderboard (/dashboard/events/[id]/leaderboard)
- Add WhatsApp share buttons on confirmation, bank instructions, volunteer view
- Enhanced Gift Aid UX with +25% bonus display and HMRC declaration text
- Gift Aid report export (HMRC-ready CSV filter)
- Volunteer view link + WhatsApp share on QR code cards
- Updated home page: 4 personas, 3 UK payment rails, 8 features
- Public event API endpoint with privacy-safe donor name truncation
- Volunteer API with stats, conversion rate, auto-refresh

CLAUDE.md

@@ -1,8 +1,5 @@
 # Pi vs CC — Extension Playground
 
-## Infrastructure Access
-**Always read `.pi/infra.md` at the start of every session** — it contains live credentials and connection details.
-
 Pi Coding Agent extension examples and experiments.
 
 ## Tooling