feat: Add configurable iStats-style menu bar modules

Replace the single "show account name" toggle with a configurable,
reorderable set of compact two-line menu bar modules: account name,
5h session usage, weekly usage, daily cost, and session/weekly reset
countdowns. Utilization renders as a monochrome progress bar (red
>90%); other values as text. Drag-to-reorder + live preview in Settings.

Implemented via NSStatusItem + NSPopover (MenuBarExtra clips tall /
multi-element labels). Strip polls every 3s since ObservableObject
delivery is unreliable for SwiftUI hosted in a status item.

Also: migration from legacy showAccountName, resilient module decode,
ET-correct double-usage promo bounds, centralized DoubleUsagePromo.