perf(blockfrost): parallelize UTxO script hydration

[wolf31o2]

Summary

• coalesce duplicate reference-script fetches within each UTxOs call
• hydrate UTxO pages with up to eight concurrent workers while preserving response order
• retain contextual UTxO failures and add HTTP coverage for deduplication, concurrency, ordering, and error context

Tests

• go test -race ./backend/blockfrost
• go test -count=1 -race ./backend/...

[Copilot]

Pull request overview

This PR improves the performance of the Blockfrost backend’s Utxos fetch path by parallelizing per-UTxO hydration while coalescing duplicate reference-script lookups within a single Utxos call, and adds HTTP tests to validate deduplication, concurrency, ordering, and error context.

Changes:

• Parallelize UTxO hydration with a bounded worker pool while preserving response order.
• Add an in-call reference script resolver to deduplicate reference-script fetches (case-insensitive hash keying).
• Add/expand HTTP tests covering deduplication, concurrency limit + ordering, and contextual error messages.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
backend/blockfrost/blockfrost.go	Adds bounded concurrent hydration for UTxO pages plus a per-call script-ref deduper used by Utxos.
backend/blockfrost/blockfrost_test.go	Adds HTTP tests for reference-script deduplication, concurrency + ordering guarantees, and error-context propagation.

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