feat(api): add hosted charge receipts

[campbellsinvestment]

Summary

• Populate existing Stripe-compatible receipt_number and receipt_url fields for new Charges using the existing dashboard URL configuration.
• Add a public hosted HTML receipt route for Charge receipts with amount, status, receipt metadata, and blockchain details when present.
• Keep delivery intentionally scoped to hosted HTML only: no email provider, no new dependency, and no dashboard/product surface.

Test plan

• NX_DAEMON=false npx nx test api
• npx prettier --check "apps/api/src/modules/Receipt.ts" "apps/api/src/modules/Charge.ts" "apps/api/src/routes/receipts.routes.ts" "apps/api/src/routes/index.ts" "apps/api/src/__tests__/Charge.spec.ts" "apps/api/src/__tests__/Receipt.spec.ts"
• npx nx lint api was attempted but this repo does not configure an api:lint target.

Notes

• Uses the existing dashboardUrl config for receipt URLs; no new env variable was added.
• Email delivery is intentionally out of scope for this PR.