feat: add PageMeta to 16 pages for SEO and proper browser tab titles

Public pages (Login, Register, Forgot/Reset Password, Verify Email,
Survey Thank You) get descriptions for SEO. Authenticated pages
(Dashboard, Flow Library, My Flows, Session History, AI Assistant,
Account Settings, Step Library, My Shares, Feedback, Guides) get
proper tab titles.

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

frontend/src/pages/AssistantChatPage.tsx

@@ -1,5 +1,6 @@
 import { useState, useEffect, useRef, useCallback } from 'react'
 import { Sparkles, Send, Loader2, Flag } from 'lucide-react'
+import { PageMeta } from '@/components/common/PageMeta'
 import { assistantChatApi } from '@/api/assistantChat'
 import { toast } from '@/lib/toast'
 import { ChatSidebar } from '@/components/assistant/ChatSidebar'
@@ -179,6 +180,8 @@ export default function AssistantChatPage() {
   }
 
   return (
+    <>
+    <PageMeta title="AI Assistant" />
     <div className="flex h-[calc(100vh-3.5rem)]">
       {/* Sidebar */}
       <ChatSidebar
@@ -303,5 +306,6 @@ export default function AssistantChatPage() {
         chatTitle={chats.find(c => c.id === activeChatId)?.title ?? 'Chat'}
       />
     </div>
+    </>
   )
 }