feat: add account management, email verification, AI fixes, and user guides

- Profile settings, account transfer, delete/leave account flows
- Email verification with JWT tokens and Resend integration
- AI assistant/copilot fixes: markdown rendering, shared RAG helpers,
  token tracking, input refocus, model_validate usage
- User guides hub + detail pages with 13 topic guides
- Sidebar and top bar navigation for guides

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

frontend/src/pages/GuidesHubPage.tsx

@@ -0,0 +1,29 @@
+import { BookOpen } from 'lucide-react'
+import { guides } from '@/data/guides'
+import { GuideCard } from '@/components/guides/GuideCard'
+
+export default function GuidesHubPage() {
+  return (
+    <div className="p-6 max-w-5xl mx-auto">
+      {/* Header */}
+      <div className="mb-8">
+        <div className="flex items-center gap-3 mb-2">
+          <div className="flex h-10 w-10 items-center justify-center rounded-xl bg-primary/10">
+            <BookOpen size={20} className="text-primary" />
+          </div>
+          <h1 className="text-2xl font-heading font-bold text-foreground">User Guides</h1>
+        </div>
+        <p className="text-sm text-muted-foreground ml-[52px]">
+          Learn how to use ResolutionFlow with step-by-step instructions for every feature.
+        </p>
+      </div>
+
+      {/* Guide cards grid */}
+      <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-4">
+        {guides.map(guide => (
+          <GuideCard key={guide.slug} guide={guide} />
+        ))}
+      </div>
+    </div>
+  )
+}