Add EMF field mode, Armory shop/waitlist, and ambient haunting layer

Three self-contained features, verified complete and cross-wired
end-to-end (audited: backend 54/54 tests, frontend 110/110 tests,
tsc --noEmit clean, i18n coverage script clean):

- EMF mode: DeviceMotion/DeviceOrientation-based field-meter sensing,
  a fifth séance channel alongside Wire/EVP/Radio/Ouija, with its own
  fragment prompt persona and full frontend gauge UI.
- Armory (shop/waitlist): pre-order capture page for the future
  Ultimate Quantum Box hardware line, rate-limited public endpoint,
  explicitly no payment collection.
- Haunting layer: ambient possession effects (dread-bed audio, title
  glitching, idle-paced whispers/manifests), respects
  prefers-reduced-motion, mounted once at the app root.

Plus WebUSB robustness fixes in lib/sdr.ts (Terratec vendor ID,
explicit selectConfiguration, isSecureContext gate).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013PphXq1s43DNRj1uWKGXof

frontend/src/components/Transcript.tsx

@@ -10,9 +10,11 @@ export type TranscriptProps = {
 }
 
 function fmtFreq(source: string, f: number): string {
-  // EVP reports Hz (voice band); radio reports MHz (FM band); wire is ambient.
+  // EVP reports Hz (voice band); radio reports MHz (FM band); emf reports a
+  // field-strength estimate; wire is ambient.
   if (source === 'evp') return `${f.toFixed(0)}Hz`
   if (source === 'radio') return `${f.toFixed(1)}MHz`
+  if (source === 'emf') return `field ${f.toFixed(2)}`
   return f >= 1000 ? `${(f / 1000).toFixed(2)}kHz` : `${f.toFixed(1)}Hz`
 }