Redesign: phosphor-terminal identity and simplified 4-page structure

Information architecture (6 nav destinations -> 4):
- New Overview home: metric strip (live setups, high confidence,
  hit rate, expectancy), top-5 setups, watchlist pulse
- Market = Watchlist + Rankings merged as tabs; scoring weights
  moved into a collapsible disclosure
- Signals = Scanner + Performance merged as tabs (Setups | Track
  Record) with actions inside the panels
- Legacy routes redirect (/watchlist, /rankings, /scanner,
  /performance)

Visual identity:
- Warm ash-green dark palette replaces cold navy; citron lime
  accent replaces blue (Tailwind gray/blue remapped at config
  level so all components reskin)
- Primary buttons: lime with ink text; long/short stays
  emerald/red
- Typography: Bricolage Grotesque display, Instrument Sans body,
  IBM Plex Mono for all numerals incl. chart canvas labels
- Atmosphere: graph-paper grid + citron glow + film grain;
  pulsing brand dot; mono-numbered nav

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/components/admin/SettingsForm.tsx

@@ -43,7 +43,7 @@ export function SettingsForm() {
               type="button"
               onClick={() => handleToggleRegistration(setting.value)}
               disabled={updateSetting.isPending}
-              className={`relative inline-flex h-6 w-11 shrink-0 cursor-pointer rounded-full border-2 border-transparent transition-colors duration-200 focus:outline-none focus:ring-2 focus:ring-blue-500 focus:ring-offset-2 focus:ring-offset-[#0a0e1a] disabled:opacity-50 ${
+              className={`relative inline-flex h-6 w-11 shrink-0 cursor-pointer rounded-full border-2 border-transparent transition-colors duration-200 focus:outline-none focus:ring-2 focus:ring-blue-500 focus:ring-offset-2 focus:ring-offset-[#0e120f] disabled:opacity-50 ${
                 setting.value === 'true' ? 'bg-gradient-to-r from-blue-600 to-sky-500' : 'bg-white/[0.1]'
               }`}
               role="switch"