Epic 6: Stories 6-2 (Markdown roundtrip) + 6-3 (Brainstorm PPTX + Canvas)

Story 6-2 — Markdown roundtrip export/import:
- lib/editor/markdown-export.ts: tiptapHTMLToMarkdown, markdownToHTML, looksLikeMarkdown
- lib/editor/markdown-paste-extension.ts: TipTap extension paste Markdown → blocs
- note-editor-toolbar.tsx: export .md + import .md (file picker)
- rich-text-editor.tsx: intégration MarkdownPasteExtension
- 40 tests unitaires markdown-export.test.ts

Story 6-3 — Brainstorm PPTX + Canvas:
- lib/brainstorm/export-pptx.ts: génération PPTX 5 slides (pptxgenjs)
- app/api/brainstorm/[sessionId]/export-pptx/route.ts: route POST protégée
- brainstorm-page.tsx: bouton PPTX, auto-select session, fix emoji, fix router.replace
- wave-canvas.tsx: fitTrigger recentrage, légende bas-droite

Onboarding activation wizard (Story 6-1):
- components/onboarding/: wizard multi-étapes, hints éditeur
- app/api/onboarding/: route PATCH onboarding
- prisma/migrations: champs onboarding user

Locales: 15 langues mises à jour (brainstorm, markdown, onboarding keys)
Sprint: 6-1 done, 6-2 review, 6-3 review

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

memento-note/components/sidebar.tsx

@@ -59,6 +59,7 @@ import {
 import { performSignOut } from '@/lib/auth-client'
 import { useBrainstormSessions, useDeleteBrainstorm } from '@/hooks/use-brainstorm'
 import { UsageMeter } from './usage-meter'
+import { StarterPackBadge } from './onboarding/starter-pack-badge'
 
 type NavigationView = 'notebooks' | 'agents' | 'reminders' | 'brainstorms' | 'revision' | 'insights'
 type SortOrder = 'newest' | 'oldest' | 'alpha' | 'manual'
@@ -1535,8 +1536,9 @@ export function Sidebar({ className, user }: { className?: string; user?: any })
           </AnimatePresence>
         </div>
 
-        {/* ── Usage meter en bas du panneau ── */}
-        <div className="border-t border-border/20 px-3 py-3 mt-auto">
+        {/* ── Usage meter + starter badge en bas du panneau ── */}
+        <div className="border-t border-border/20 px-3 py-3 mt-auto space-y-2">
+          <StarterPackBadge />
           <UsageMeter />
         </div>