feat: complete Quantumancy web app — full frontend + docs

Frontend (React 18 + TS + Vite):
- Landing: glitching hero, live /api/stats veil ticker, mode cards, featured spirits
- Séance: three.js shader ghost (hue/form per entity, mood + audio-reactive),
  Ouija planchette board spelling utterances, transcript with TTS replay,
  entity dossier, direct contact streaming, passive/active listening
- Modes: Wire Ghost telemetry panel, EVP mic anomaly detection, WebUSB
  RTL-SDR sweep + waterfall (hardware pass pending), Ouija/Direct Contact
- Codex: public registry + entity dossiers, rarity tiers, i18n EN/ES complete
- State: VeilSocket (reconnect/backoff), seance reducer, auth context
- 72 vitest tests green; served by FastAPI at :7777

Docs: README + as-built plans 3-7

frontend/src/pages/EnterPage.tsx

@@ -0,0 +1,129 @@
+// Enter page: the threshold. Gothic auth panel floating in CSS fog —
+// toggles between Reconnect (login) and First contact (register), and
+// steps the medium through to the séance on success.
+
+import { useState } from 'react'
+import type { FormEvent } from 'react'
+import { Navigate, useNavigate } from 'react-router-dom'
+import { useTranslation } from 'react-i18next'
+import { useAuth } from '../state/auth'
+import './EnterPage.css'
+
+type EnterMode = 'login' | 'register'
+
+export function EnterPage() {
+  const { t } = useTranslation()
+  const { user, login, register } = useAuth()
+  const navigate = useNavigate()
+
+  const [mode, setMode] = useState<EnterMode>('login')
+  const [username, setUsername] = useState('')
+  const [password, setPassword] = useState('')
+  const [error, setError] = useState<string | null>(null)
+  const [busy, setBusy] = useState(false)
+
+  // Already seated at the table — no need to knock again.
+  if (user) {
+    return <Navigate to="/seance" replace />
+  }
+
+  const switchMode = (next: EnterMode) => {
+    setMode(next)
+    setError(null)
+  }
+
+  const handleSubmit = async (event: FormEvent<HTMLFormElement>) => {
+    event.preventDefault()
+    if (busy) return
+    setError(null)
+    setBusy(true)
+    try {
+      if (mode === 'register') {
+        await register(username, password)
+      } else {
+        await login(username, password)
+      }
+      navigate('/seance')
+    } catch (err) {
+      setError(err instanceof Error ? err.message : String(err))
+      setBusy(false)
+    }
+  }
+
+  return (
+    <div className="enter-page">
+      <div className="enter-fog" aria-hidden="true" />
+      <div className="enter-scanlines" aria-hidden="true" />
+
+      <main className="enter-panel">
+        <h1 className="enter-title">{t('nav.home')}</h1>
+        <p className="enter-sub">
+          {mode === 'login' ? t('enter.reconnectSub') : t('enter.firstContactSub')}
+        </p>
+
+        <div className="enter-tabs" role="tablist">
+          <button
+            type="button"
+            role="tab"
+            aria-selected={mode === 'login'}
+            className={`enter-tab${mode === 'login' ? ' active' : ''}`}
+            onClick={() => switchMode('login')}
+          >
+            {t('enter.reconnect')}
+          </button>
+          <button
+            type="button"
+            role="tab"
+            aria-selected={mode === 'register'}
+            className={`enter-tab${mode === 'register' ? ' active' : ''}`}
+            onClick={() => switchMode('register')}
+          >
+            {t('enter.firstContact')}
+          </button>
+        </div>
+
+        <form className="enter-form" onSubmit={handleSubmit}>
+          <label className="enter-field">
+            <span>{t('enter.username')}</span>
+            <input
+              type="text"
+              value={username}
+              onChange={(e) => setUsername(e.target.value)}
+              required
+              minLength={3}
+              autoComplete="username"
+              autoFocus
+            />
+          </label>
+          <label className="enter-field">
+            <span>{t('enter.password')}</span>
+            <input
+              type="password"
+              value={password}
+              onChange={(e) => setPassword(e.target.value)}
+              required
+              minLength={8}
+              autoComplete={mode === 'login' ? 'current-password' : 'new-password'}
+            />
+          </label>
+
+          {error && (
+            <p className="enter-error" role="alert">
+              {t('enter.failed', { message: error })}
+            </p>
+          )}
+
+          <button type="submit" className="enter-submit" disabled={busy}>
+            {mode === 'login' ? t('enter.submitLogin') : t('enter.submitRegister')}
+          </button>
+        </form>
+
+        <p className="enter-smallprint">
+          {t('enter.smallPrint', {
+            defaultValue: 'your medium handle is only ever stored on this server',
+          })}
+        </p>
+      </main>
+    </div>
+  )
+}