Remove dead Stripe integration

Stripe was wired up but never used:
- No STRIPE_SECRET_KEY in .env
- Card payment step had a 'simulated fallback' that pretended to charge
- Stripe fees (1.4% + 20p) contradict '100% goes to charity' brand promise
- Bank transfer is the primary rail, GoCardless (DD) is the secondary

Removed:
- src/lib/stripe.ts (Stripe client, checkout sessions, webhooks)
- src/app/api/stripe/checkout/route.ts
- src/app/api/stripe/webhook/route.ts
- src/app/p/[token]/steps/card-payment-step.tsx (263 lines)
- 'stripe' and '@stripe/stripe-js' npm packages
- Card option from PaymentStep (payment-step.tsx)
- Card references from confirmation-step.tsx, success/page.tsx
- Stripe from landing page integrations grid
- Stripe from privacy policy sub-processors
- Stripe from terms of service payment references

Type Rail changed: 'bank' | 'gocardless' | 'card' → 'bank' | 'gocardless'
Pledge flow bundle: 19.5kB → 18.2kB (-1.3kB)

Payment options donors now see:
1. Bank Transfer (recommended, zero fees)
2. Direct Debit via GoCardless (1% + 20p, hassle-free)

pledge-now-pay-later/package-lock.json

@@ -11,7 +11,6 @@
         "@auth/prisma-adapter": "^2.11.1",
         "@prisma/adapter-pg": "^7.4.2",
         "@prisma/client": "^7.4.2",
-        "@stripe/stripe-js": "^8.8.0",
         "@types/bcryptjs": "^2.4.6",
         "@types/qrcode": "^1.5.6",
         "bcryptjs": "^3.0.3",
@@ -29,7 +28,6 @@
         "react": "^18",
         "react-dom": "^18",
         "sharp": "^0.34.5",
-        "stripe": "^20.4.0",
         "tailwind-merge": "^3.5.0",
         "zod": "^4.3.6"
       },
@@ -1794,15 +1792,6 @@
       "integrity": "sha512-l2aFy5jALhniG5HgqrD6jXLi/rUWrKvqN/qJx6yoJsgKhblVd+iqqU4RCXavm/jPityDo5TCvKMnpjKnOriy0w==",
       "license": "MIT"
     },
-    "node_modules/@stripe/stripe-js": {
-      "version": "8.8.0",
-      "resolved": "https://registry.npmjs.org/@stripe/stripe-js/-/stripe-js-8.8.0.tgz",
-      "integrity": "sha512-NNYuyW8qmLjyHnpyFgs/23wUrjB8k0xN9YIZFOMLewCa/pIkIji9e9aY/EgdNryEDDRptc6TcPIHRvG1R0ClFw==",
-      "license": "MIT",
-      "engines": {
-        "node": ">=12.16"
-      }
-    },
     "node_modules/@swc/counter": {
       "version": "0.1.3",
       "resolved": "https://registry.npmjs.org/@swc/counter/-/counter-0.1.3.tgz",
@@ -7792,23 +7781,6 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
-    "node_modules/stripe": {
-      "version": "20.4.0",
-      "resolved": "https://registry.npmjs.org/stripe/-/stripe-20.4.0.tgz",
-      "integrity": "sha512-F/aN1IQ9vHmlyLNi3DkiIbyzQb6gyBG0uYFd/VrEVQSc9BLtlgknPUx0EvzZdBMRLFuRaPFIFd7Mxwtg7Pbwzw==",
-      "license": "MIT",
-      "engines": {
-        "node": ">=16"
-      },
-      "peerDependencies": {
-        "@types/node": ">=16"
-      },
-      "peerDependenciesMeta": {
-        "@types/node": {
-          "optional": true
-        }
-      }
-    },
     "node_modules/styled-jsx": {
       "version": "5.1.1",
       "resolved": "https://registry.npmjs.org/styled-jsx/-/styled-jsx-5.1.1.tgz",