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/app/api/brainstorm/[sessionId]/update-position/route.ts

@@ -0,0 +1,50 @@
+import { NextRequest, NextResponse } from 'next/server'
+import prisma from '@/lib/prisma'
+import { auth } from '@/auth'
+import { z } from 'zod'
+
+const positionSchema = z.object({
+  ideaId: z.string().min(1),
+  positionX: z.number(),
+  positionY: z.number(),
+})
+
+export async function POST(
+  request: NextRequest,
+  { params }: { params: Promise<{ sessionId: string }> }
+) {
+  const session = await auth()
+  if (!session?.user?.id) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+  }
+
+  try {
+    const { sessionId } = await params
+    const body = await request.json()
+    const { ideaId, positionX, positionY } = positionSchema.parse(body)
+
+    const brainstormSession = await prisma.brainstormSession.findFirst({
+      where: { id: sessionId, userId: session.user.id },
+    })
+
+    if (!brainstormSession) {
+      return NextResponse.json({ error: 'Session not found' }, { status: 404 })
+    }
+
+    await prisma.brainstormIdea.update({
+      where: { id: ideaId },
+      data: { positionX, positionY },
+    })
+
+    return NextResponse.json({ success: true })
+  } catch (error: any) {
+    if (error instanceof z.ZodError) {
+      return NextResponse.json({ error: error.issues }, { status: 400 })
+    }
+    console.error('Error updating position:', error)
+    return NextResponse.json(
+      { error: error.message || 'Failed to update position' },
+      { status: 500 }
+    )
+  }
+}