Render a wiring diagram as SVG or PNG

Public, CORS-open endpoint; 30 requests per minute per client IP. The client IP is the first X-Forwarded-For entry, else X-Real-IP, else one shared unknown bucket; counters are kept in memory per server instance and per route. Flat mode renders loads, batteries and chargers. When circuits is non-empty the flat lists are ignored and one labelled panel per circuit is rendered, with links drawn as connectors; links whose from/to resolve to no circuit or to the same circuit are dropped. A power source is added automatically for each charger based on its sourceType, and fuses/protection components are added when batteries and loads exist. Accept: image/png returns PNG, anything else SVG; when PNG conversion fails the SVG is returned instead. Component icons from iconUrl are fetched server-side and embedded as data URIs. No external API is called.