feat: Implement Token Sale

[0xNeshi]

IMPORTANT: The PR will need minor updating once https://github.com/openZeppelin/contractsSui/pull/417 is merged.
Other than the current use of Coin for the boundary with VestingWallet, the PR is ready for review.

Resolves #319

PR Checklist

• Tests
• Documentation
• Changelog

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.26%. Comparing base (23af906) to head (efcd351).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #414   +/-   ##
=======================================
  Coverage   83.26%   83.26%           
=======================================
  Files          29       29           
  Lines        2307     2307           
  Branches      732      731    -1     
=======================================
  Hits         1921     1921           
  Misses        348      348           
  Partials       38       38           

Flag	Coverage Δ
contracts/access	65.46% <ø> (ø)
contracts/allowance	52.00% <ø> (ø)
contracts/finance	25.57% <ø> (ø)
contracts/utils	44.09% <ø> (ø)
math/fixed_point	60.22% <ø> (ø)

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[bidzyyys]

Review — sale

• 🟡 prefunded_sale.move:847 (share_and_activate) — the module doc guarantees "buyer claims and refunds do not depend on admin liveness" (L48), but the paired RefundVault is shared only by a separate integrator step (refund_vault::share) that the library neither performs nor verifies. Activate without sharing the vault and it stays owned by the issuer, so the permissionless cancel_after_close / refund paths (which need &mut vault) become uncallable by buyers — silent in the success path (claim needs no vault), locking buyer funds only on a soft-cap miss → have share_and_activate take the RefundVault<PaymentCoin> by value, assert object::id(vault) == *refund_vault_id.borrow(), and share_object it, so the no-admin-liveness guarantee is structural rather than convention.