add gitt issues bounty-queue command

[dataCenter430]

Problem

The smart contract exposes get_bounty_queue() -> Vec<u64> which returns the ordered list of issue IDs currently in the payout queue. This is not surfaced anywhere in the CLI, so validators and admins have no way to inspect the queue from the terminal.

Proposed Solution

Add a new gitt issues bounty-queue command:

gitt issues bounty-queue
gitt issues bounty-queue --json

Expected output: a table (or JSON array) of issue IDs that are queued for payout, in order.