fix: restore brainstorming feature with missing socket server and real-time events

memento-note/app/api/brainstorm/[sessionId]/finalize/route.ts

@@ -1,6 +1,8 @@
 import { NextRequest, NextResponse } from 'next/server'
 import prisma from '@/lib/prisma'
 import { auth } from '@/auth'
+import { logActivity } from '@/lib/brainstorm-collab'
+import { emitToSession } from '@/lib/socket-emit'
 
 export async function POST(
   request: NextRequest,
@@ -80,6 +82,15 @@ export async function POST(
     const dry = Array.from(noteImpactMap.values()).filter(n => n.acceptedCount === 0 && n.dismissedCount > 0).length
     const totalRefs = Array.from(noteImpactMap.values()).length
 
+    await logActivity(sessionId, 'session_finalized', session.user.id, { notesEnriched: fruitful, notesMarkedDry: dry })
+
+    await emitToSession(sessionId, 'activity:new', {
+      action: 'session_finalized',
+      userId: session.user.id,
+      userName: session.user.name || 'Guest',
+      details: { notesEnriched: fruitful, notesMarkedDry: dry }
+    })
+
     return NextResponse.json({
       success: true,
       impact: {