v0.8 preview — modern UI redesign

Full UI overhaul: a top app bar (city/date, play/pause, speed, ⋮ menu for New/Save/Load/Budget/Eval/Tax), the Funds/Population/Score HUD, a tool palette bottom sheet with tools grouped by category and real icons, and clean Move/Build + Preview controls. The old 27-button bottom row is gone. Install: download the .apk, open, allow unknown sources.