feat: brainstorm sessions, PDF document Q&A, embedding fixes, and UI improvements

- Add brainstorm feature with collaborative canvas, AI idea generation, live cursors, playback, and export
- Add PDF upload/extraction/ingestion pipeline with pgvector document search (RAG)
- Add document Q&A overlay with streaming chat and PDF preview
- Add note attachments UI with status polling, grid layout, and auto-scroll
- Add task extraction AI tool and agent executor improvements
- Fix NoteEmbedding missing updatedAt column, re-index 66 notes with 1536-dim embeddings
- Fix brainstorm 'Create Note' button: add success toast and redirect to created note
- Fix memory echo notification infinite polling
- Fix chat route to always include document_search tool
- Add brainstorm i18n keys across all 14 locales
- Add socket server for real-time brainstorm collaboration
- Add hierarchical notebook selector and organize notebook dialog improvements
- Add sidebar brainstorm section with session management
- Update prisma schema with brainstorm tables, attachments, and document chunks

memento-note/lib/socket-emit.ts

@@ -0,0 +1,27 @@
+// [UPDATE - TEMPS RÉEL] Helper pour émettre des événements Socket.io depuis les API routes Next.js.
+// Utilise un canal HTTP interne vers le process socket-server.ts séparé.
+// Non-fatal : en cas d'échec, le client récupérera l'état via React Query polling.
+
+export async function emitToSession(
+  sessionId: string,
+  event: string,
+  data: unknown
+): Promise<void> {
+  const socketUrl = process.env.SOCKET_INTERNAL_URL || 'http://localhost:3003'
+  const internalKey = process.env.SOCKET_INTERNAL_KEY || ''
+
+  try {
+    await fetch(`${socketUrl}/emit`, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        'x-internal-key': internalKey,
+      },
+      body: JSON.stringify({ sessionId, event, data }),
+      signal: AbortSignal.timeout(2000), // 2s max — ne pas bloquer l'API
+    })
+  } catch {
+    // Non-fatal — le canal Socket est best-effort
+    // Le client se resynchronise via invalidation React Query
+  }
+}