Render every diagram of a multi-diagram project

Public, CORS-open endpoint; 30 requests per minute per client IP (counted separately from /api/diagram/generate). 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. Each entry of diagrams is rendered as its own SVG. Each bridge adds a virtual load to the diagram whose id equals fromDiagramId and a virtual charger plus power source to the diagram whose id equals toDiagramId. The response is always JSON; with Accept: image/png each diagram additionally carries a base64 PNG (null when not requested or when conversion failed). Component icons are embedded as in /api/diagram/generate. No external API is called.