Configure deposit cap on subscriptions

[hpmaxi]

Priority

Medium — should be addressed soon

User story / Problem statement

The vault accepts deposits without limit. RWA funds operating under regulatory exemptions or finite off-chain investment capacity need an upper bound on deposits to prevent over-subscription before capital can be deployed.

Expected outcome

Governance can configure an asset deposit cap for the vault. Deposits exceeding the cap are refused. If unset (default), the cap is effectively infinite, preserving existing unbounded behaviour.

Acceptance criteria

• Deposit cap defaults to infinite (None / unbounded) on initialization.
• Governance can set, update, or clear the deposit cap via admin entrypoint (set_deposit_cap).
• A public getter (deposit_cap) returns the current configured cap.
• request_deposit reverts if accepting the deposit would breach the cap.
• Emits an event when the deposit cap is updated.
• Unit tests verify cap enforcement at boundary values, updates by governance, and unauthorized rejection.

Technical notes

The cap bounds total deposited capital across epochs or active economic assets. Setting the cap to None or an unconstrained value restores unbounded deposits without breaking existing callers or deployments.

Refs: Tranche 1 deliverables (deposit cap)