fix: 5 bugs critiques de l'éditeur (Phase 1 audit)

1. replaceAll (Find & Replace) — une seule transaction ProseMirror
   au lieu d'un forEach cassé. Tous les matchs sont maintenant remplacés.

2. Link Preview unwrap — deleteNode() au lieu de clearer les attrs
   qui laissaient un nœud fantôme invisible dans le document.

3. Conversion Markdown → richtext — breaks: true dans marked.parse()
   Les simple newlines sont maintenant convertis en <br>.
   + préserve les blocs custom (toggle, callout, math, columns,
   outline, link-preview) en commentaires HTML lors de l'export MD.

4. emitNoteChange exercices — shape corrigée (type:'created' attend
   un objet Note, pas noteId/notebookId séparés).

5. Raccourcis clavier sans conflit :
   Cmd+Shift+C → Cmd+Alt+C (callout, avant: copier)
   Cmd+Shift+O → Cmd+Alt+O (outline, avant: historique/signets)
   Cmd+Shift+L → Cmd+Alt+L (colonnes, avant: lock screen macOS)

memento-note/prisma/migrations/20260620120000_add_plan_entitlement/migration.sql

@@ -0,0 +1,68 @@
+-- CreateTable
+CREATE TABLE IF NOT EXISTS "PlanEntitlement" (
+    "id" TEXT NOT NULL,
+    "tier" "SubscriptionTier" NOT NULL,
+    "feature" TEXT NOT NULL,
+    "limitValue" INTEGER,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT "PlanEntitlement_pkey" PRIMARY KEY ("id")
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS "PlanEntitlement_tier_feature_key" ON "PlanEntitlement"("tier", "feature");
+CREATE INDEX IF NOT EXISTS "PlanEntitlement_tier_idx" ON "PlanEntitlement"("tier");
+
+-- Seed defaults (only when table is empty)
+INSERT INTO "PlanEntitlement" ("id", "tier", "feature", "limitValue")
+SELECT v.id, v.tier::"SubscriptionTier", v.feature, v."limitValue"
+FROM (VALUES
+  ('pe-basic-semantic_search', 'BASIC', 'semantic_search', 30),
+  ('pe-basic-auto_tag', 'BASIC', 'auto_tag', 15),
+  ('pe-basic-auto_title', 'BASIC', 'auto_title', 5),
+  ('pe-basic-brainstorm_create', 'BASIC', 'brainstorm_create', 1),
+  ('pe-basic-brainstorm_expand', 'BASIC', 'brainstorm_expand', 10),
+  ('pe-basic-brainstorm_enrich', 'BASIC', 'brainstorm_enrich', 20),
+  ('pe-basic-suggest_charts', 'BASIC', 'suggest_charts', 5),
+  ('pe-basic-ai_flashcard', 'BASIC', 'ai_flashcard', 5),
+  ('pe-basic-voice_transcribe', 'BASIC', 'voice_transcribe', 20),
+  ('pe-pro-semantic_search', 'PRO', 'semantic_search', 200),
+  ('pe-pro-auto_tag', 'PRO', 'auto_tag', 500),
+  ('pe-pro-auto_title', 'PRO', 'auto_title', 200),
+  ('pe-pro-reformulate', 'PRO', 'reformulate', 50),
+  ('pe-pro-chat', 'PRO', 'chat', 50),
+  ('pe-pro-brainstorm_create', 'PRO', 'brainstorm_create', 5),
+  ('pe-pro-brainstorm_expand', 'PRO', 'brainstorm_expand', 100),
+  ('pe-pro-brainstorm_enrich', 'PRO', 'brainstorm_enrich', 200),
+  ('pe-pro-suggest_charts', 'PRO', 'suggest_charts', 50),
+  ('pe-pro-slide_generate', 'PRO', 'slide_generate', 20),
+  ('pe-pro-excalidraw_generate', 'PRO', 'excalidraw_generate', 20),
+  ('pe-pro-ai_flashcard', 'PRO', 'ai_flashcard', 100),
+  ('pe-pro-voice_transcribe', 'PRO', 'voice_transcribe', 500),
+  ('pe-business-semantic_search', 'BUSINESS', 'semantic_search', 1000),
+  ('pe-business-auto_tag', 'BUSINESS', 'auto_tag', 1000),
+  ('pe-business-auto_title', 'BUSINESS', 'auto_title', 1000),
+  ('pe-business-reformulate', 'BUSINESS', 'reformulate', 500),
+  ('pe-business-chat', 'BUSINESS', 'chat', 500),
+  ('pe-business-brainstorm_create', 'BUSINESS', 'brainstorm_create', NULL),
+  ('pe-business-brainstorm_expand', 'BUSINESS', 'brainstorm_expand', 500),
+  ('pe-business-brainstorm_enrich', 'BUSINESS', 'brainstorm_enrich', 1000),
+  ('pe-business-suggest_charts', 'BUSINESS', 'suggest_charts', 200),
+  ('pe-business-slide_generate', 'BUSINESS', 'slide_generate', 100),
+  ('pe-business-excalidraw_generate', 'BUSINESS', 'excalidraw_generate', 100),
+  ('pe-business-ai_flashcard', 'BUSINESS', 'ai_flashcard', NULL),
+  ('pe-business-voice_transcribe', 'BUSINESS', 'voice_transcribe', NULL),
+  ('pe-enterprise-semantic_search', 'ENTERPRISE', 'semantic_search', NULL),
+  ('pe-enterprise-auto_tag', 'ENTERPRISE', 'auto_tag', NULL),
+  ('pe-enterprise-auto_title', 'ENTERPRISE', 'auto_title', NULL),
+  ('pe-enterprise-reformulate', 'ENTERPRISE', 'reformulate', NULL),
+  ('pe-enterprise-chat', 'ENTERPRISE', 'chat', NULL),
+  ('pe-enterprise-brainstorm_create', 'ENTERPRISE', 'brainstorm_create', NULL),
+  ('pe-enterprise-brainstorm_expand', 'ENTERPRISE', 'brainstorm_expand', NULL),
+  ('pe-enterprise-brainstorm_enrich', 'ENTERPRISE', 'brainstorm_enrich', NULL),
+  ('pe-enterprise-suggest_charts', 'ENTERPRISE', 'suggest_charts', NULL),
+  ('pe-enterprise-slide_generate', 'ENTERPRISE', 'slide_generate', NULL),
+  ('pe-enterprise-excalidraw_generate', 'ENTERPRISE', 'excalidraw_generate', NULL),
+  ('pe-enterprise-ai_flashcard', 'ENTERPRISE', 'ai_flashcard', NULL),
+  ('pe-enterprise-voice_transcribe', 'ENTERPRISE', 'voice_transcribe', NULL)
+) AS v(id, tier, feature, "limitValue")
+WHERE NOT EXISTS (SELECT 1 FROM "PlanEntitlement" LIMIT 1);

memento-note/prisma/schema.prisma

@@ -820,6 +820,18 @@ model FeatureFlag {
   updatedAt DateTime @updatedAt
 }
 
+model PlanEntitlement {
+  id         String           @id @default(cuid())
+  tier       SubscriptionTier
+  feature    String
+  limitValue Int?
+  createdAt  DateTime         @default(now())
+  updatedAt  DateTime         @updatedAt
+
+  @@unique([tier, feature])
+  @@index([tier])
+}
+
 // ===== CLUSTERING & BRIDGE NOTES =====
 
 model NoteCluster {