feat: Phase 1 Aether Drift — mobile-first grid layout and token migration
Replace Discord flex layout with CSS Grid on desktop (312px sidebar +
1fr main) and overlay drawer on mobile. Migrate all discord-* class
references to Aether Drift design tokens across 15 files (~200 refs).
Layout: ServerSidebar becomes a fixed glass strip (md:glass-strip),
ChannelSidebar gets pl-[72px] offset, bottom bar is a glass-bubble
(z-105), MessageInput floats as absolute glass pill on desktop (z-110).
MemberSidebar/ActivityPanel hidden on mobile via hidden md:block.
Z-index stack: MobileNav backdrop z-35, sidebar z-40, glass strip z-100,
bottom bar z-105, input bubble z-110, hamburger z-120, profile popout
z-145, device panels z-150, modals z-200.
Jannis Braun
79252fe54a