Harden caller authorization and precondition guards in admin_override_streaming_release

[godamongstmen897]

Problem & Goal

Add the authorization and precondition checks at the top of admin_override_streaming_release so the function rejects unauthorized callers and illegal source states before it reads or writes any ledger entry.

Context & Components

• Target Repository: escrow-contract
• Module/Component: admin_override_streaming_release (Admin override releasing a streamed milestone payment)

Implementation Details

1. Review the existing codebase inside the escrow-contract directory.
2. Locate the source files relating to admin_override_streaming_release.
3. Implement the feature logic/validation rules step-by-step.
4. Ensure code conforms to codebase patterns (lints, formats, types).

Verification & Testing Requirements

• Validation check: Assert an unauthorized caller and an illegal source state each return their specific typed error, and that no storage entry is mutated in either case.
• Add comprehensive test cases matching these validation requirements.
• Ensure all other existing project tests continue to compile and pass.

---

Note: This issue is completely self-contained and does not block or require any other issues to be resolved.

[faithalabi6-cyber]

@faithalabi6-cyber has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi maintainer, I'm new to this platform and yet to receive any issue, please assign

ℹ️ Repo Maintainers: To accept this application, review their application or assign @faithalabi6-cyber to this issue.

[qa-eden]

@qa-eden has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi maintainer, I would work on this

ℹ️ Repo Maintainers: To accept this application, review their application or assign @qa-eden to this issue.

[DevFaster]

@DevFaster has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

hi repo maintainer. please assign me this issue . i will fix this issue correctly.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @DevFaster to this issue.