Add /email route as standalone web email client; v1.1.11

Extracts the email inbox from /admin and builds it as a full-viewport
email client at /email with the same admin auth. Key improvements over
the old embedded panel:

- Full-height split-pane layout (sidebar list + detail pane)
- Subject line extracted and shown separately for inbound emails
- Inline reply composer inside the detail pane (no more page-jump)
- Compose-new button for outbound messages to arbitrary addresses
- Search/filter across name, email, subject, and body
- Unread dot indicators with localStorage tracking (marks read on open)
- Keyboard navigation: ↑/↓ or j/k to move, r to reply, e to archive, Esc to close
- Source badges (contact-form / inbound-email) on list items
- Sent history and reply templates accessible via footer drawers
- 30-second polling for new messages
- New POST /api/admin-email/compose server endpoint for outbound sends
- Dashboard card "Open Inbox" now links to /email

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

src/App.tsx

@@ -2,6 +2,7 @@ import { useState, useEffect, useRef } from 'react'
 import type { ReactElement } from 'react'
 import { Link, NavLink, Routes, Route, useLocation, useNavigate, useParams } from 'react-router-dom'
 import AdminPage from './AdminPage'
+import EmailShell from './EmailPage'
 import QASection from './components/QASection'
 import ContactForm from './components/ContactForm'
 import { ColossiansStudyIndexPage, ColossiansStudyNotesPage, ColossiansStudySectionPage, StudyLandingPage, StudySignupPage, StudyAccountPage, StudyCommunityPage, StudyQuizPage } from './colossiansStudy'
@@ -2494,6 +2495,7 @@ export default function App() {
       <Route path="/subscribe/thanks" element={<SubscribeThankYouPage />} />
       <Route path="/certificate/:token" element={<PublicCertificatePage />} />
       <Route path="/admin" element={<AdminShell content={content} onSave={setContent} />} />
+      <Route path="/email" element={<EmailShell />} />
       <Route path="/preview" element={<PreviewPage />} />
       <Route
         path="/privacy"