feat: /data-api hub — 9 benches, by-benchmark + by-provider pivot

[Flotapponnier]

Summary

• New /data-api page aggregating 9 existing benchmarks across 5 categories: price feeds, token metadata, portfolio/wallet, DEX coverage, NFT data
• Blob-only data loading (same pattern as /rpc): loads bench CDN blobs in parallel, no Prometheus at render time, graceful degradation to "warming up" state
• Two tabs: By Benchmark (grouped tables with leader, runners-up, per-region and per-chain breakdown) and By Provider (cross-bench pivot with rank badges per group)
• KPI strip: unique providers, active benchmarks, headline price feed leader, fastest wallet indexing
• Group summary pills above the tabs showing current leader per category
• Added "Data APIs" nav link to site-header between Benchmarks and Products

Files added

• src/lib/data-api-stats.ts — cohort builder with fetchDataApiSnapshot (unstable_cache 60s)
• src/app/data-api/page.tsx — server component, JSON-LD breadcrumb + ItemList
• src/components/data-api-hub-tabs.tsx — client tab wrapper
• src/components/data-api-bench-groups.tsx — "By Benchmark" grouped tables with region/chain strips
• src/components/data-api-providers-pivot.tsx — "By Provider" sortable cross-bench pivot

Test plan

• Check /data-api renders with warming-up state if blobs aren't loaded yet
• Verify both tabs work and sorting on pivot works
• Check nav "Data APIs" link highlights correctly on /data-api
• Confirm build has no TS errors (already verified locally)