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/components/guides/GuideCard.tsx

@@ -0,0 +1,34 @@
+import { Link } from 'react-router-dom'
+import type { Guide } from '@/data/guides'
+
+interface GuideCardProps {
+  guide: Guide
+}
+
+export function GuideCard({ guide }: GuideCardProps) {
+  const Icon = guide.icon
+
+  return (
+    <Link
+      to={`/guides/${guide.slug}`}
+      className="glass-card block rounded-2xl p-5 transition-all"
+    >
+      <div className="flex items-start gap-3.5">
+        <div className="flex h-10 w-10 shrink-0 items-center justify-center rounded-xl bg-primary/10">
+          <Icon size={20} className="text-primary" />
+        </div>
+        <div className="min-w-0">
+          <h3 className="text-sm font-heading font-semibold text-foreground mb-1">
+            {guide.title}
+          </h3>
+          <p className="text-xs text-muted-foreground leading-relaxed">
+            {guide.summary}
+          </p>
+          <span className="mt-2 inline-block font-label text-[0.625rem] uppercase tracking-[0.1em] text-primary">
+            {guide.sections.length} {guide.sections.length === 1 ? 'section' : 'sections'}
+          </span>
+        </div>
+      </div>
+    </Link>
+  )
+}