replace PNPL abbreviation with full name in all user-facing copy

- Landing page: 'PNPL captures...' → 'Pledge Now, Pay Later captures...'
- Landing page: 'Who uses PNPL?' → 'Who uses Pledge Now, Pay Later?'
- Landing page: rewrote HNW + fundraiser descriptions to avoid abbreviation
- Dashboard sidebar fallback: 'PNPL' → 'Pledge Now, Pay Later'
- Bank reference prefixes (PNPL-XXXX-50) left as-is — 18-char BACS limit

pledge-now-pay-later/src/app/dashboard/layout.tsx

@@ -33,7 +33,7 @@ export default function DashboardLayout({ children }: { children: React.ReactNod
               <span className="text-white font-bold text-sm">P</span>
             </div>
             <div className="hidden sm:block">
-              <span className="font-black text-sm text-gray-900">{user?.orgName || "PNPL"}</span>
+              <span className="font-black text-sm text-gray-900">{user?.orgName || "Pledge Now, Pay Later"}</span>
             </div>
           </Link>
           <div className="flex-1" />