DataLoader batching for GraphQL + query budgets in CI

[tayebmokni]

Summary

Implement per-request DataLoader batching for GraphQL resolvers per doc 07 §17.3. For the post → author → comments shape, GraphQL resolvers use dataloader to batch and cache N+1 queries. REST endpoints get explicit IN (...) batch fetches in code (code review rejects N+1). Add an integration test harness with pg_stat_statements to enforce a "query count budget" per endpoint (e.g., /blog/[slug] <= 4 queries) — CI fails on breach.

Design reference

• docs/07-media-performance.md §17.3

Acceptance criteria

• dataloader integrated into GraphQL request context (dataloader.New(req, ...))
• User, comment, term, media loaders registered with batch size 100
• userLoader, commentLoader, termLoader, mediaLoader use WHERE id = ANY($1) queries
• Test harness with pg_stat_statements records query count per endpoint
• Query-count budgets declared per endpoint; CI fails on breach
• /blog/[slug] <= 4 queries; /blog index <= 6 queries; /category/[slug] <= 5 queries

Dependencies

none

Complexity

M

[tayebmokni]

Closing — shipped in the final-wave PR (#487-#492). Auto-close only fires for first ref.