refactor: simplify JS/CSS — ~96 lines removed, 11/11 tests pass
- LeafletControl: fix 3 overlapping buttons (added top offsets), remove ZONE_LABEL_MAP duplication, wire locate button
- index.tsx: eliminate loading state (derive from !bands), remove no-op zoom handlers, remove redundant map div style
- components.tsx: replace Floater with MapSizeFixer, consolidate duplicate isWithdrawn, replace setTimeout scroll with useEffect, fix Legend/ BandRow colors via constants, stable BandRow keys
- types.ts: remove dead ZoneMap, single new Date() in getCurrentActiveZone, eliminate dt2p/timeToMinutes duplication, fix filterBands single-loop, retain Brussels bounding box for zoom quality
- index.css: remove 16 lines dead .sidebar CSS