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/components/brainstorm/live-cursors.tsx

@@ -0,0 +1,93 @@
+'use client'
+
+import React from 'react'
+import { PresenceUser } from '@/hooks/use-brainstorm-socket'
+
+function Cursor({ x, y, name, color }: { x: number; y: number; name: string; color: string }) {
+  return (
+    <div
+      className="absolute pointer-events-none z-50 transition-all duration-75"
+      style={{ transform: `translate(${x}px, ${y}px)` }}
+    >
+      <svg width="16" height="16" viewBox="0 0 16 16" fill="none">
+        <path d="M0 0L16 6L8 8L6 16L0 0Z" fill={color} />
+      </svg>
+      <div
+        className="mt-3 ml-3 px-2 py-0.5 rounded-full text-[10px] font-bold text-white whitespace-nowrap shadow-lg"
+        style={{ backgroundColor: color }}
+      >
+        {name}
+      </div>
+    </div>
+  )
+}
+
+export function LiveCursors({ others }: { others: PresenceUser[] }) {
+  return (
+    <div className="absolute inset-0 pointer-events-none z-50">
+      {others.map((user) => {
+        if (!user.cursor) return null
+        return (
+          <Cursor
+            key={user.userId}
+            x={user.cursor.x}
+            y={user.cursor.y}
+            name={user.name}
+            color={user.color}
+          />
+        )
+      })}
+    </div>
+  )
+}
+
+export function useCursorTracking(
+  containerRef: React.RefObject<HTMLDivElement | null>,
+  moveCursor: (cursor: { x: number; y: number } | null) => void
+) {
+  React.useEffect(() => {
+    const container = containerRef.current
+    if (!container) return
+
+    const handleMove = (e: MouseEvent) => {
+      const rect = container.getBoundingClientRect()
+      moveCursor({ x: e.clientX - rect.left, y: e.clientY - rect.top })
+    }
+
+    const handleLeave = () => {
+      moveCursor(null)
+    }
+
+    container.addEventListener('mousemove', handleMove)
+    container.addEventListener('mouseleave', handleLeave)
+    return () => {
+      container.removeEventListener('mousemove', handleMove)
+      container.removeEventListener('mouseleave', handleLeave)
+    }
+  }, [containerRef, moveCursor])
+}
+
+export function PresenceAvatars({ others }: { others: PresenceUser[] }) {
+  if (others.length === 0) return null
+
+  return (
+    <div className="flex items-center gap-1">
+      {others.slice(0, 4).map((user) => {
+        const initial = (user.name || '?').charAt(0).toUpperCase()
+        return (
+          <div
+            key={user.userId}
+            className="w-6 h-6 rounded-full flex items-center justify-center text-[9px] font-bold text-white border-2 border-white dark:border-zinc-900 shadow-sm"
+            style={{ backgroundColor: user.color, marginLeft: '-6px' }}
+            title={user.name}
+          >
+            {initial}
+          </div>
+        )
+      })}
+      {others.length > 4 && (
+        <span className="text-[9px] text-muted-foreground ml-1">+{others.length - 4}</span>
+      )}
+    </div>
+  )
+}