Fix(block): avoid prevout fan-out for tx values

[NateIsern]

Motivation

• Prevent the /api/block endpoint from triggering expensive prevout enrichment and RPC/Mongo amplification when it only needs per-transaction total output values.

Description

• When computing txValues in server/index.ts, pass prevoutLookupBudget: { remaining: 0 } to blockCache.getTransaction so enrichInputPrevouts is not invoked.

Testing

• Ran bun run typecheck and bun run test, and both completed successfully.

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Codex Task

[cursor]

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