`forward_ton_amount` stuck on Jetton Wallet if receiver has inbound disabled

[Andrew Gutarev]

In the current Tact implementation of the governance jetton (based on the stablecoin-contract), the same known issue from the reference contract persists: if a recipient’s jetton wallet has inbound messages disabled, the forward_ton_amount sent during transfer remains stuck on the sender’s jetton wallet.
The bounce handler does not refund the TON to the owner, and there is no function to manually withdraw excess TON.

This issue is noted in the original stablecoin-contract documentation:
https://github.com/ton-blockchain/stablecoin-contract?tab=readme-ov-file#notes

Part of #152