Add responsive layout for tablet and phone screen sizes

Three new breakpoints plus modifications to the existing 600px one:

768px — topbar wraps to two rows, topbarRight fills second row,
  container/card padding tightens, brand + logo shrink slightly.

480px — subtitle hidden, refresh label hidden, spoolman link hidden,
  topbar badges compact; printerHead stacks vertically; CFS box header
  narrows to 40px with vertical-rl text, spool pods shrink to 44px;
  stats grid columns tighten; jobs spool rows wrap.

360px — grams column hidden in stats table to preserve layout on the
  smallest Android screens.

JS: badge text shortened at <480px ("Printer: connected" → "Connected",
  "Printers: 2/2 online" → "2/2", "CFS: 1 detected" → "CFS: 1").

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>