Marketing site, legal drafts and developer documentation preview

Added

• The public marketing site: product pages, solution pages, pricing, trust and contact forms.
• First drafts of the legal documents, including the electronic signature consent and the ACH authorization. All drafts are pending counsel review.
• A preview of the developer documentation: authentication, webhooks, rate limits, errors, a placeholder API reference and CSV import formats.
• A public verification page for signed documents. It shows a result only when a verification record exists.

Notes

The API reference describes a preview schema. Endpoints and fields will change before the API is released.