RT-23 Config Loading Methods

All supported methods for loading map configurations: div attributes, URL parameters, function calls, share mechanics.

Test plan: 23-config-loading-methods.md

default-config.html — Default config loading: empty div, malformed JSON, invalid properties, URL params, data-config-url, createMapFromConfigFast
demo-flood.html — data-lang="fr" + inline data-config, multi-language
demo-custom-footer-height.html — Custom footer heights (400px, 100vh)