Add gateway.kilo.ai rewrites for LLM and indexing routes

[iscekic]

Summary

• Adds beforeFiles rewrites to proxy LLM gateway and code-indexing routes to gateway.kilo.ai when KILO_GATEWAY_BACKEND is not set
• Routes proxied: /api/openrouter/*, /api/gateway/*, /api/models/stats, /api/models/stats/*, /api/modelstats, /api/models/up, /api/defaults, /api/code-indexing/upsert-by-file
• Follows the same pattern as the existing GLOBAL_KILO_BACKEND / global-api.kilo.ai rewrites
• The gateway deployment itself should have KILO_GATEWAY_BACKEND=true set so it serves these routes locally

Notes

• This PR should be merged after the gateway Vercel project is created and the deploy job PR (Add deploy-gateway job to production workflow #651) is merged, so traffic doesn't route to a nonexistent backend
• FIM completions stays on global-api.kilo.ai — unchanged

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Notes

• The new gatewayApiRewrites block correctly follows the same pattern as the existing globalApiRewrites — conditional on KILO_GATEWAY_BACKEND !== 'true', using beforeFiles to proxy before local filesystem routes.
• All 8 proxied routes (/api/openrouter/*, /api/gateway/*, /api/models/stats, /api/models/stats/*, /api/modelstats, /api/models/up, /api/defaults, /api/code-indexing/upsert-by-file) have corresponding local API route handlers that will serve traffic when KILO_GATEWAY_BACKEND=true.
• Route ordering is correct: exact /api/models/stats match is listed before the /api/models/stats/:path* wildcard.

Files Reviewed (1 file)

• next.config.mjs - 0 issues