Fix resubmit burn crash recovery and concurrent-push safety

[dylanuys]

Summary

• Persist the exact signed burn transaction, hash, chain identity, amount, and intended submission before broadcast, using private atomic/fsynced files. A failed write prevents broadcast.
• Recover pending burns from finalized chain history and reuse confirmed proof through upload retries. Unknown outcomes, corrupt state, and contradictory execution events block a fresh burn.
• Lock the full upload/burn workflow per hotkey/subnet across local processes and threads, including proof acceptance and cleanup.
• Display the actual alpha amount, up to 2% price padding, and additional transaction fees before confirmation. Apply durable signing to both burn_alpha and add_stake_burn.

Protection requires preserving the same local GAS_HOME; it is not a cross-machine exactly-once guarantee. Missing transactions remain blocked even after expiry and require investigation. Confirmed on-chain failures permit a newly authorized attempt on the next run. Recovery behavior and limits are documented.

Validation

• Full subnet suite: 197 tests passed.
• CI Ruff rules and git diff --check passed.
• Fault injection covers crash/timeout before and after broadcast, disk/fsync failures, malformed/mismatched state, ambiguous receipts/events, concurrent CLI processes, and upload retries. Transaction hashing checked against the installed SDK.
• No live burn transactions submitted.