Reduce redundant database round trips in list and summary API endpoints

[masa-57]

Summary

Several API endpoints execute multiple serial count and list queries that can likely be consolidated.

Evidence

• issues separate queries for paged L2 results, total L2 count, unclustered groups, unclustered count, total image count, and total L1 count.
• , , and follow the common pattern in separate round trips.

Why this matters

These extra round trips add latency on high-traffic list endpoints and make the API layer harder to optimize consistently.

Suggested direction

• Audit list endpoints for avoidable count queries and repeated summary lookups
• Consolidate counts where practical, or compute them in a dedicated service/query object
• Benchmark before/after on representative data volumes