feat(indexer): ingest bounty chain events

[Thanhdn1984]

Implements bounty chain event ingestion for issue #76.\n\nChanges:\n- Adds typed Bounty event/action parsing for post/claim/dispute/resolve/cancel flows.\n- Maps parsed bounty tx kinds/details into indexer transaction records.\n- Extracts sender/participant fields for poster, attester, disputer, resolver/canceller flows.\n- Extends indexer DB handling for all bounty variants.\n\nValidation:\n- PASS: cargo test -p ligate-api-indexer classify_recognises_bounty --quiet\n- PASS: cargo test -p ligate-api-indexer --quiet (25 unit + 1 integration)\n- Full workspace cargo test --quiet is blocked in this env by missing risc0 toolchain for sov-risc0-adapter: Is risc0 installed? If not you can install it with the rzup tool.\n\nDiff/test logs archived locally in money-work/20260529_0030.

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