fix: Remove combined transferable and regular coins

[jprzimba]

Add support for atomically removing coins across two coin types (primary then secondary).

• Introduce Account::removeCoins overload to remove an amount using two distinct coin types and register separate transactions for each type.
• Implement AccountRepositoryDB::removeCoins to lock rows, deduct from primary then secondary, record transactions, and return proper AccountErrors_t results; add DB helper executeWithinTransactionRollbackOnFailure to simplify transactional operations.
• Update account repository header and in-memory test fixture to support the new removeCoins API.
• Update gamestore Lua and player logic to treat transferable + regular Tibia coins as a combined balance (send total to older clients, add canPayForOffer logic, and prefer combined removal when paying transferable offers); add Lua binding Player:removeTransferableAndTibiaCoins.
• Adjust Player methods to propagate actual removal result and send balance updates only on success.
• Add unit tests to verify combined removal, insufficient funds behavior, and repository failure handling.

These changes allow transferable-coin offers to be paid using transferable coins first and regular coins as a fallback, while ensuring consistency via transactional DB updates and updated APIs.