Create and cancel a redemption request

[luchobonatti]

User story / Problem statement

An investor exits by escrowing shares. Losing the allowlist must not close that door.

Expected outcome

A redemption request escrows shares, and cancelling returns them to a listed controller.

Acceptance criteria

• The request does not check the allowlist
• It is refused when a request is already open on either side
• Cancel is offered while pending and gone once priced
• A delisted investor cannot cancel back to shares, and is told so before signing

Technical notes

Blocked by #65. Blocked by #85. Parent: #30.