[ENG-1509] Fix /v4/fills/parentSubaccount query performance (backport #3279)

[mergify]

Problem

The /v4/fills/parentSubaccountNumber endpoint was timing out for users with large fill histories. Root cause: using IN (subquery) to find fills across parent + child subaccounts caused Postgres to misestimate row counts and choose a catastrophically inefficient query plan—scanning millions of rows instead of using optimal index scans.

Why this happens:

When Postgres plans a query with IN (SELECT ...), it must estimate the subquery's cardinality before execution. For our subaccount lookup, it estimated ~314 rows when the actual result was 5.3M fills (testing with the subaccount causing the issue). This caused Postgres to:

1. Fetch ALL fills for ALL child subaccounts
2. Sort the entire result set
3. Only then apply the LIMIT

With explicit UUIDs, Postgres can use "Index Scan Backward" per subaccount and stop early at the LIMIT.

Fix:

Resolve subaccount IDs to concrete UUIDs in a separate query before the main fills query, replacing the inline subquery.

Testing:

Tested on testnet indexer database (240M fills) against address dydx1qzq0dx4xjj06d4nxfx7ls53d8wru625s445mhs— with 5.3M fills in subaccount 0.
Query performance comparison using EXPLAIN ANALYZE:

Approach	Execution Time	Rows Scanned	Pages Read
IN (subquery)	195s	5,306,867	962,324
IN (Explicit UUIDs)	280ms	~13,807	~2,500

With the "subaccountId" IN (Explicit UUIDs) approach,

Summary by CodeRabbit

• Refactor

  • Replaced subquery-based subaccount filtering with pre-resolved subaccount ID filtering for faster, more efficient retrieval.

• New Features

  • Added a public subaccount ID lookup to resolve related subaccounts for a given parent.

• Chores

  • CI workflow updated to trigger builds for an additional development branch.

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This is an automatic backport of pull request #3279 done by [Mergify](https://mergify.com).

[linear]

ENG-1509 Check on testnet indexer load

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