fix: add get_version() and upgrade() to vouching-contract

[EmeditWeb]

Problem

The vouching contract is missing two functions that every other contract has:

• get_version() — returns current version symbol
• upgrade() — admin-only WASM update

Contract impact: The vouching contract cannot be upgraded or version-checked. If a bug is found in the vouching logic, the contract must be replaced entirely (new deployment, new address), breaking all existing vouch references.

Before Starting

Read: context/architecture-context.md

Root Cause

The functions were omitted when the vouching contract was implemented.

What To Build

1. Add get_version(env: Env) -> Symbol returning e.g. symbol_short!("1_0_0")
2. Add upgrade(env: Env, admin: Address, new_wasm_hash: BytesN<32>) with auth and reentrancy guard
3. Write tests for both functions

Files To Touch

• contracts/vouching-contract/src/lib.rs — add get_version and upgrade

Acceptance Criteria

• get_version returns a version symbol
• upgrade allows authorized WASM update
• upgrade requires admin auth
• All existing tests pass

Mandatory Checks

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

[Iker2522]

I have extensive experience writing smart contracts in Soroban / Rust and implementing upgradeability patterns. I reviewed contracts/vouching-contract/src/lib.rs and understand how the missing upgrade hooks break maintainability. I will implement the get_version() and upgrade() functions with strict admin authentication, integrate reentrancy guards, add full test coverage for the upgrade flow, and submit a verified PR within 1 day.