[Contract] Guild Treasury Withdrawal Cap (Per Transaction)

[gabito1451]

Independence Note: Write this as a checking function inside a mock test scenario.

Context:
To mitigate impact of admin keys being compromised, we want a hard cap on how much can be withdrawn in a single transaction from the guild treasury.

Objective:
Implement a maximum withdrawal amount check.

Acceptance Criteria:

• Add a max_withdrawal parameter in the Guild Configuration.
• In the withdraw function, assert that amount <= max_withdrawal.
• Return a custom ErrorCode::LimitExceeded if the amount is too high.
• Include unit tests attempting to withdraw amounts both below and over the limit.

Technical Pointers:

• This provides an extra layer of protection for the guild's long-term sustainability.