Adds Reporting for Steam Failed Trades

[Step7750]

It's possible for a Steam trade to hit status 4 (failed) upon offer acceptance.

This PR will push notary proofs if the related trade is for a CSFloat sale, allowing the platform to gracefully handle it.

Ref CSF-1701

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Note

Medium Risk
Changes trade verification and notary submission for pending CSFloat sales; failures are mitigated by feature flags and the same backoff used for rollback proofs, but incorrect matching could affect trade state handling.

Overview
Adds detection and reporting when a Steam trade reaches failed status while a related CSFloat sale is still pending with an active offer.

The periodic CSFloat trade ping now runs pingFailedTrades after trade history is fetched. findFailedTrades links failed Steam history entries to pending trades by asset ID and counterparty, skipping trades already marked with steam_trade_failed_id or with an accepted offer. When background notary rollback is enabled, it submits proofs through the existing proveTradesInBackground path (with the same 60-minute backoff on proof failure).

Trade history fetching now requests and retains failed entries (includeFailed on the Steam API, status filter, and include_failed: true on notary prove requests). SlimTrade gains optional steam_trade_failed_id for deduplication. Unit tests cover the matching rules.

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