- Add upstream_connections_per_host config option (default: 20) - Implement per-host semaphores to limit concurrent connections - Semaphore released when response body is closed - Prevents overwhelming origin servers with parallel requests
- Add image proxy config options (signing_key, whitelist_hosts, allow_http) - Create Service to orchestrate cache, fetcher, and processor - Initialize image service in handlers OnStart hook - Implement HandleImage with URL parsing, signature validation, cache - Implement HandleRobotsTxt for search engine prevention - Parse query params for signature, quality, and fit mode