Multi-building demo, Recalculate action, hide feedback panel #99

Extended the demo config from 1 to 4 buildings (varied type/construction period/country/envelope) so the map shows distinct, clickable buildings instead of one hardcoded box. Renamed the Apply button to Recalculate (same behavior: commits the draft, runs BuEM via buem-gateway, stores results for download). Removed the feedback/testing-session side panel, not needed for this demo. Split the load-profile download into three zipped CSVs. Fixed the dummy buildings' construction_period values to match labels ignis's period picker actually recognises.