fix: expose get_admin() in vendor-registry-contract

[EmeditWeb]

Problem

The vendor registry contract stores the admin address (storage.rs line 17) but does NOT expose it as a public function in the #[contractimpl] block. All other contracts expose get_admin(). Without it, external callers cannot determine who controls the vendor registry.

Before Starting

Read: context/architecture-context.md

Root Cause

The function was omitted when exposing the public interface.

What To Build

1. Add pub fn get_admin(env: Env) -> Address to the contract impl in lib.rs
2. Delegate to storage::get_admin()

Files To Touch

• contracts/vendor-registry-contract/src/lib.rs — add get_admin

Acceptance Criteria

• get_admin returns the admin address
• Works without auth (read-only)
• All existing tests pass

Mandatory Checks

• context/ files read
• cargo build passes
• cargo test passes
• PR references this issue

[playmaker410]

Hi Maintainer,

I’d love to take this on. I have hands-on experience with Rust, Soroban, Cairo, and TypeScript, and I’m confident I can deliver a solid solution within 24 hours.