Settings dialog: responsive sizing, scale-based type hierarchy (no
bold/uppercase emphasis), semantic icon accents, InkWell-backed nav
with reliable hover and click cursors, and consistent vertical rhythm.

Map theming now lives in one place: a single profile list under
Current strategy with inline management, plus a live-preview editor
dialog (real map + dot grid re-rendered as colors change). Strategy
overrides are labeled "This strategy only", promotable to profiles,
and guarded by a confirm before being discarded. Built-in profiles
are tagged. The duplicated SVG color mapper is extracted and shared
by the canvas, screenshot exporter, and preview.