feat: bloc Toggle/Section repliable + infrastructure embeddings par fragments

- Nouveau bloc Toggle : sections dépliables dans l'éditeur (slash menu + drag handle)
  - Transformer un bloc existant en section repliable via le menu d'action
  - Boutons désactiver (unwrap) et supprimer dans l'en-tête
  - i18n FR/EN complet
- Infrastructure embeddings par fragments (inspiré AppFlowy)
  - Table NoteEmbeddingChunk + index HNSW
  - Chunking sémantique (~1000 chars, overlap 200, dedup par hash)
  - Indexation incrémentale au save (createNote + updateNote + clip)
  - Queue concurrence 4, retry backoff exponentiel

memento-note/app/api/clip/save/route.ts

@@ -6,6 +6,7 @@ import { createNotification } from '@/app/actions/notifications'
 import { buildClipSourceFooter, clipFooterLocaleTag } from '@/lib/clip/extract-article'
 import { resolveClipLocale, wrapClipArticleHtml, applyRtlToHtmlBlocks } from '@/lib/clip/rtl-content'
 import { embeddingService } from '@/lib/ai/services/embedding.service'
+import { chunkIndexingService } from '@/lib/ai/services/chunk-indexing.service'
 import { upsertNoteEmbedding } from '@/lib/embeddings'
 import DOMPurify from 'isomorphic-dompurify'
 
@@ -92,6 +93,8 @@ export async function POST(request: NextRequest) {
         if (embedding?.length) {
           await upsertNoteEmbedding(note.id, embedding)
         }
+
+        await chunkIndexingService.indexNote(note.id, title || domain, fullContent)
       } catch (error) {
         console.error('[clip/save] embedding generation failed:', error)
       }