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/notes/[id]/attachments/[attachmentId]/route.ts

@@ -0,0 +1,87 @@
+import { NextRequest, NextResponse } from 'next/server'
+import prisma from '@/lib/prisma'
+import { auth } from '@/auth'
+import fs from 'fs'
+
+export async function GET(
+  request: NextRequest,
+  { params }: { params: Promise<{ id: string; attachmentId: string }> }
+) {
+  const session = await auth()
+  if (!session?.user?.id) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+  }
+
+  try {
+    const { id: noteId, attachmentId } = await params
+
+    const download = request.nextUrl.searchParams.get('download')
+
+    const attachment = await prisma.noteAttachment.findFirst({
+      where: { id: attachmentId, noteId, note: { userId: session.user.id } },
+      include: download ? undefined : {
+        chunks: {
+          select: { id: true, chunkIndex: true, pageNumber: true },
+          orderBy: { chunkIndex: 'asc' },
+        },
+      },
+    })
+
+    if (!attachment) {
+      return NextResponse.json({ error: 'Not found' }, { status: 404 })
+    }
+
+    if (download) {
+      if (!fs.existsSync(attachment.filePath)) {
+        return NextResponse.json({ error: 'File not found' }, { status: 404 })
+      }
+      const fileBuffer = fs.readFileSync(attachment.filePath)
+      return new NextResponse(fileBuffer, {
+        headers: {
+          'Content-Type': attachment.mimeType || 'application/pdf',
+          'Content-Disposition': `inline; filename="${attachment.fileName}"`,
+        },
+      })
+    }
+
+    return NextResponse.json({ success: true, data: attachment })
+  } catch (error) {
+    console.error('Error fetching attachment:', error)
+    return NextResponse.json({ error: 'Failed to fetch attachment' }, { status: 500 })
+  }
+}
+
+export async function DELETE(
+  request: NextRequest,
+  { params }: { params: Promise<{ id: string; attachmentId: string }> }
+) {
+  const session = await auth()
+  if (!session?.user?.id) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+  }
+
+  try {
+    const { id: noteId, attachmentId } = await params
+
+    const attachment = await prisma.noteAttachment.findFirst({
+      where: { id: attachmentId, noteId, note: { userId: session.user.id } },
+    })
+
+    if (!attachment) {
+      return NextResponse.json({ error: 'Not found' }, { status: 404 })
+    }
+
+    try {
+      if (fs.existsSync(attachment.filePath)) {
+        fs.unlinkSync(attachment.filePath)
+      }
+    } catch {}
+
+    await prisma.noteAttachment.delete({ where: { id: attachmentId } })
+
+    return NextResponse.json({ success: true })
+  } catch (error) {
+    console.error('Error deleting attachment:', error)
+    return NextResponse.json({ error: 'Failed to delete attachment' }, { status: 500 })
+  }
+}