Implement pre-funding term edits via `PUT /escrow/single-release/v2/update`

[grantfox-oss]

Context

Before an escrow is funded, the admin may need to correct terms (amount, roles, fee, milestones) set at deploy time.

Task

Add an admin-only action calling PUT /escrow/single-release/v2/update with the full escrow payload. Note this is a full replace, restricted to the admin role, and:

• If the escrow is unfunded, all properties can be changed.
• If the escrow is already funded, only adding milestones is allowed — everything else is locked by the API.

Sign and submit the returned unsignedXdr.

Acceptance criteria

• Action only exposed to the admin wallet/role.
• UI reflects the funded/unfunded constraint (disables locked fields once the escrow has funds).

[GBOYEE]

Hi — pre-funding term edits via PUT /escrow/single-release/v2/update are a common ops need and currently missing. I can add an admin-only action that does the full payload replace, gated to unfunded escrows (and partially restricted once funded), with the role check enforced server-side. I'd like to claim this.

[QuiqueCode]

Proposal: Admin Escrow Update Action

Understanding

Add an admin-only action to correct escrow terms before/after funding by calling PUT /escrow/single-release/v2/update with the full escrow payload. If unfunded, all properties are editable; if funded, only adding milestones is allowed, everything else locked. Sign and submit the returned unsignedXdr.

Plan

• Gate the action so it's only exposed to the admin wallet/role.
• Build the update form/action to submit the full escrow payload as required by the full-replace endpoint.
• Read the escrow's funded/unfunded state and reflect it in the UI: unfunded all fields enabled; funded only the add-milestone control enabled, remaining fields disabled.
• On submit, call PUT /escrow/single-release/v2/update, receive the unsignedXdr, sign it, and submit the signed transaction.

Looking forward to working on this.

[grantfox-oss]

🦊 GrantFox — @QuiqueCode has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #314)
2. Your PR will be reviewed by the Kaizenode maintainers

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