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]/invite/route.ts

@@ -0,0 +1,123 @@
+import { NextRequest, NextResponse } from 'next/server'
+import prisma from '@/lib/prisma'
+import { auth } from '@/auth'
+import { z } from 'zod'
+import crypto from 'crypto'
+import { verifyParticipant, logActivity } from '@/lib/brainstorm-collab'
+
+const inviteSchema = z.object({
+  role: z.enum(['editor', 'viewer']).default('editor'),
+  expiresInHours: z.number().min(1).max(168).default(24),
+  email: z.string().email().optional(),
+})
+
+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 { isParticipant } = await verifyParticipant(sessionId, session.user.id, 'host')
+
+    if (!isParticipant) {
+      return NextResponse.json({ error: 'Only the host can invite' }, { status: 403 })
+    }
+
+    const body = await request.json()
+    const { role: inviteRole, expiresInHours, email } = inviteSchema.parse(body)
+
+    const brainstormSession = await prisma.brainstormSession.findUnique({
+      where: { id: sessionId },
+      select: { id: true, seedIdea: true, userId: true, inviteToken: true, inviteExpiry: true },
+    })
+
+    if (!brainstormSession) {
+      return NextResponse.json({ error: 'Session not found' }, { status: 404 })
+    }
+
+    let token = brainstormSession.inviteToken
+    let expiry = brainstormSession.inviteExpiry
+
+    if (!token || (expiry && expiry < new Date())) {
+      token = crypto.randomBytes(24).toString('hex')
+      expiry = new Date(Date.now() + expiresInHours * 60 * 60 * 1000)
+      await prisma.brainstormSession.update({
+        where: { id: sessionId },
+        data: { inviteToken: token, inviteExpiry: expiry },
+      })
+    }
+
+    const inviteUrl = `/brainstorm?invite=${token}`
+
+    if (email) {
+      const recipient = await prisma.user.findUnique({
+        where: { email },
+        select: { id: true, name: true, email: true },
+      })
+
+      if (!recipient) {
+        return NextResponse.json({ error: 'User not found' }, { status: 404 })
+      }
+
+      if (recipient.id === session.user.id) {
+        return NextResponse.json({ error: 'Cannot invite yourself' }, { status: 400 })
+      }
+
+      const existing = await prisma.brainstormParticipant.findFirst({
+        where: { sessionId, userId: recipient.id },
+      })
+
+      if (existing) {
+        return NextResponse.json({ error: 'Already a participant' }, { status: 409 })
+      }
+
+      await prisma.notification.create({
+        data: {
+          userId: recipient.id,
+          type: 'brainstorm_invite',
+          title: brainstormSession.seedIdea.length > 50
+            ? brainstormSession.seedIdea.substring(0, 50) + '…'
+            : brainstormSession.seedIdea,
+          message: `${session.user.name || 'Someone'} invited you to a brainstorm session`,
+          actionUrl: inviteUrl,
+          relatedId: sessionId,
+        },
+      })
+
+      await logActivity(sessionId, 'invite_created', session.user.id, {
+        role: inviteRole,
+        targetEmail: email,
+        targetUserId: recipient.id,
+      })
+
+      return NextResponse.json({
+        success: true,
+        mode: 'email',
+        invitedUser: { name: recipient.name, email: recipient.email },
+        inviteUrl,
+        expiresAt: expiry,
+      })
+    }
+
+    await logActivity(sessionId, 'invite_created', session.user.id, { role: inviteRole })
+
+    return NextResponse.json({
+      success: true,
+      mode: 'link',
+      inviteUrl,
+      token,
+      expiresAt: expiry,
+    })
+  } catch (error: any) {
+    if (error instanceof z.ZodError) {
+      return NextResponse.json({ error: error.issues }, { status: 400 })
+    }
+    console.error('Error creating invite:', error)
+    return NextResponse.json({ error: 'Failed to create invite' }, { status: 500 })
+  }
+}