feat(treasury): transfer tokens on deposit (#656)

[meshmesh001]

Summary

This PR resolves issue #656 by implementing real token transfers in the treasury deposit entrypoint, replacing the previous no-op implementation.

Changes Made

1. Token Transfer & Custody:

   • Updated deposit(e: Env, from: Address, token: Address, amount: u64) -> Result<(), TreasuryError> to accept a token: Address parameter.
   • Enforced token allowlist verification (DataKey::TokenAllowlist), rejecting any token not on the allowlist with TreasuryError::TokenNotAllowed before pause/auth checks.
   • Enforced pause checks (check_not_paused) and caller authentication (from.require_auth()).
   • Implemented real token movement into treasury custody using the Soroban token interface: token::Client::new(&e, &token).transfer(&from, &e.current_contract_address(), &(amount as i128)).

2. Event Emission:

   • Added deposit(env: &Env, token: &Address, from: &Address, amount: &u64) helper in COMEBACKHERE-contracts/contracts/treasury/src/events.rs.
   • Emitted deposit event upon successful deposit with (token, from, amount).

3. ABI & Documentation Updates:

   • Regenerated abis/treasury.json ABI snapshots including the new deposit event and public function declarations.
   • Updated docs/error-codes.md documentation for TreasuryError::TokenNotAllowed.
   • Fixed CONTRACTS_ROOT directory resolution in scripts/generate_abi_metadata.py.

4. Unit Tests:

   • Added unit tests using register_stellar_asset_contract_v2 verifying balance changes before and after deposit.
   • Added unit tests for paused state rejection and non-allowlisted token rejection paths.
   • Added test verifying event emission on deposit.

Existing Callers

• comebackhere-frontend/src/components/TreasuryManager.tsx already constructs arguments [from, token, stroops] when submitting deposits.
• frontend/src/components/TreasuryManagerPage/TreasuryManagerPage.tsx submits { token, amount } to /treasury/deposit.
• README.md sequence diagram lists deposit interaction.

Closes #656
Closes #656
Closes #656
Closes #656

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