Nuevo Proposals

Proposals preview for site admins

Internal: the Proposals area from docs/specs/PROPOSALS.md is built and open to site admins only.

Internal: Proposals (/proposals) is built as a site-admin preview (ProposalsPolicy::MEMBERS_ENABLED is false): the editor, 17 built-in templates, team templates, saved sections, the price list, JSON import and export, sending with access codes and scheduled sends, approvals, the client page at /proposal/{token} with choices, questions, signing and deposit payment, signed PDFs and certificates, after-acceptance actions, reports and settings. Contacts show their proposals to site admins. The assistant does not read proposals yet (CoverageExclusions).