chore: remove image-generation feature

Remove the entire image-generation feature and its integration with
the landing backend. This feature was not in active use and is being
removed as part of codebase cleanup.

Removed:
- features/image-generation/ service, shared types, and documentation
- features/landing/backend/src/image-generation/ integration module

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

features/portal/frontend/package.json

@@ -10,6 +10,7 @@
     "preview": "vite preview"
   },
   "dependencies": {
+    "@lilith/email-users": "workspace:*",
     "@tanstack/react-query": "^5.62.0",
     "clsx": "^2.1.1",
     "date-fns": "^4.1.0",

features/portal/frontend/src/App.tsx

@@ -1,9 +1,12 @@
 import { Routes, Route, NavLink } from 'react-router-dom';
 import { InboxPage } from './features/inbox/InboxPage';
+import { EmailAddressesPage, EmailPreferencesPage } from '@lilith/email-users';
 import clsx from 'clsx';
 
 const navItems = [
   { to: '/', label: 'Inbox' },
+  { to: '/email/addresses', label: 'Email Addresses' },
+  { to: '/email/preferences', label: 'Email Preferences' },
 ];
 
 export function App() {
@@ -45,6 +48,8 @@ export function App() {
       <main className="flex-1 p-8 overflow-auto">
         <Routes>
           <Route path="/" element={<InboxPage />} />
+          <Route path="/email/addresses" element={<EmailAddressesPage profileId="temp-profile-id" />} />
+          <Route path="/email/preferences" element={<EmailPreferencesPage />} />
         </Routes>
       </main>
     </div>