feat(brainstorm): UX fixes — modal confirmation + destination carnet + race fix

UX Pro Max appliqué selon les best practices 2026 (Heptabase, Obsidian, Tana):
- confirmation-dialogs (HIGH): modal de confirmation avant brainstorm
- success-feedback (MEDIUM): toast avec destination du carnet
- nav-state-active (MEDIUM): indication claire de la session active

3 fixes:

1. Modal de confirmation (brainstorm-confirm-dialog.tsx, 181 lignes):
   - Design system respecté: brand-accent, memento-paper, font-memento-serif
   - Aperçu seed en card paper
   - Sélecteur de carnet avec animation d'expansion
   - Bouton 'Annuler' + 'Lancer le brainstorm' avec loader
   - role=dialog, aria-modal, aria-label
   - focus-visible, keyboard nav
   - backdrop-blur-sm + click-to-close
   - Lazy loaded via next/dynamic

2. Race condition fix (brainstorm-page.tsx L111):
   - Auto-select session désactivé si urlSeed présent
   - urlSeed + urlInviteToken court-circuitent le useEffect

3. Toast avec destination (handleConvert + noteCreatedIn key):
   - message: 'Note créée dans [Nom du carnet]'
   - useConvertIdea accepte notebookId optionnel
   - API convert accepte notebookId via zod schema
   - useConvertIdea(mutationFn) accepte string | {ideaId, notebookId}

i18n: 9 nouvelles clés brainstorm.* en EN/FR

memento-note/components/notes-list-views.tsx

@@ -50,6 +50,8 @@ import {
 } from 'lucide-react'
 import { cn } from '@/lib/utils'
 import { useHydrated } from '@/lib/use-hydrated'
+import dynamic from 'next/dynamic'
+const BrainstormConfirmDialog = dynamic(() => import('@/components/brainstorm/brainstorm-confirm-dialog').then(m => ({ default: m.BrainstormConfirmDialog })), { ssr: false })
 import { formatDistanceToNow } from 'date-fns'
 import { fr } from 'date-fns/locale/fr'
 import { enUS } from 'date-fns/locale/en-US'
@@ -715,14 +717,23 @@ const GridCard = memo(function GridCard({
   aiIllustrationEnabled,
   onOpen,
   onTogglePin,
-  onDeleteNote,
-  onMoveToNotebook,
+  onDeleteNote,  onMoveToNotebook,
   onNoteIllustrationGenerated,
   onNoteIllustrationDeleted,
   onOpenHistory,
   isOverlay = false,
 }: GridCardSharedProps) {
   const router = useRouter()
+  const [brainstormNote, setBrainstormNote] = useState<Note | null>(null)
+
+  const handleBrainstormConfirm = (notebookId: string | null) => {
+    if (!brainstormNote) return
+    const seed = `${brainstormNote.title || untitled}\n\n${getNotePlainExcerpt(brainstormNote, 200)}`.trim()
+    const params = new URLSearchParams({ seed: seed.slice(0, 300), sourceNoteId: brainstormNote.id })
+    if (notebookId) params.set('notebookId', notebookId)
+    router.push(`/brainstorm?${params.toString()}`)
+    setBrainstormNote(null)
+  }
   const { t, language } = useLanguage()
   const hydrated = useHydrated()
   const title = getNoteDisplayTitle(note, untitled)
@@ -741,11 +752,11 @@ const GridCard = memo(function GridCard({
 
   const handleBrainstormClick = (e: React.MouseEvent) => {
     e.stopPropagation()
-    const seed = `${title}\n\n${excerpt}`.trim() || title
-    router.push(`/brainstorm?seed=${encodeURIComponent(seed.slice(0, 300))}&sourceNoteId=${note.id}`)
+    setBrainstormNote(note)
   }
 
   return (
+    <>
     <motion.div
       initial={isOverlay || !hydrated ? false : { opacity: 0, y: 15 }}
       animate={isOverlay ? undefined : { opacity: 1, y: 0 }}
@@ -851,5 +862,13 @@ const GridCard = memo(function GridCard({
         </div>
       </div>
     </motion.div>
+
+      <BrainstormConfirmDialog
+        open={brainstormNote !== null}
+        onClose={() => setBrainstormNote(null)}
+        onConfirm={(notebookId) => { if (brainstormNote) handleBrainstormConfirm(notebookId) }}
+        note={brainstormNote}
+      />
+    </>
   )
 })