Avoid wasted startup work for non-tech variants and reduce per-render
cost in buildLayers():
- Remove eager rebuildTechHQSupercluster/rebuildDatacenterSupercluster
from map load and basemap-switch handlers; build lazily in
updateClusterData() only when the exact conditions are met
- Add WeakMap-backed filterByTimeCached() with 1-minute time bucket;
replaces 10 inline filterByTime() calls in buildLayers()
- Rewrite GlobeMap.initStaticLayers() to delegate to
ensureStaticDataForLayer(), skipping datasets for disabled layers;
hook into setLayers() and enableLayer() for lazy init on first enable
