feat(bitcoin): Add indexing UTXO on event

[Azzurriii]

• Added UTXO event structure and related methods for tracking created and spent UTXOs.
• Enhanced BitcoinIndexer to extract UTXO events from transactions and include them in block metadata.
• Updated MempoolWorker to process and emit UTXO events for monitored addresses.
• Modified emitter to support UTXO event emission to NATS.
• Refactored Block type to include metadata for better extensibility.

[anhthii]

revert c24bb6e , not necessary

Additional feedback:

Mempool should not emit UTXOs. UTXOs are used for balance calculation and spending decisions. Mempool txs can be dropped or replaced (RBF), making mempool
UTXOs unreliable. If a consumer spends a UTXO from a mempool tx that never confirms, the spending tx fails. Mempool worker should only emit transfer events
(for UI notifications), not UTXOs.

[anhthii]

❯ go run cmd/indexer/main.go index --chains=bitcoin_testnet --debug --manual
2026-02-19T18:16:29+07:00 INF Config loaded environment=development
2026-02-19T18:16:29+07:00 INF Connecting to redis url=localhost:6379 environment=development mtls=false
2026-02-19T18:16:29+07:00 INF Connected to Redis pong=PONG
2026-02-19T18:16:29+07:00 INF Redis connection established
2026-02-19T18:16:29+07:00 INF Database connection skipped - not configured
2026-02-19T18:16:29+07:00 INF Connecting to kvstore url=127.0.0.1:8500
2026-02-19T18:16:29+07:00 INF Connecting to NATS url=nats://localhost:4222
2026-02-19T18:16:29+07:00 INF NATS connection established
2026-02-19T18:16:29+07:00 INF Stream found name=transfer subjects=[transfer.event.*] state=0
2026-02-19T18:16:29+07:00 ERR Error creating JetStream stream: !BADKEY="nats: API error: code=400 err_code=10065 description=subjects overlap with an

NATS JetStream is rejecting a stream creation because the subjects it wants to use are already claimed by another existing stream.

Fix create a separate stream for utxo without deleting and recreating transfer stream that can cause lost of unconsumed messages
a19577d