feat: RefBoard v0.4.0 — collaborative reference board with layers, groups & polished UI

Full-featured PureRef-style collaborative canvas for game dev teams:
- Layer panel with visibility, lock, drag reorder, group/ungroup (Ctrl+G/Shift+G)
- Arrangement tools (grid, row, column) via right-click context menu
- Copy to system clipboard (Ctrl+C writes PNG for external paste in Paint etc.)
- Number shortcuts (1-5) for tool selection with visible shortcut badges
- Premium dark UI across all pages (Login, Collections, Boards, Editor)
- Socket.IO rooms for cursors, transforms, and presence notifications
- MinIO image storage with backend proxy, drag/drop and paste upload

backend/socket/board-room.js

@@ -0,0 +1,142 @@
+const { getBoard, getCollection, getCollectionMember } = require('../db');
+
+// Track active users per room: Map<roomName, Map<userId, userInfo>>
+const activeUsers = new Map();
+
+function getRoomName(boardId) {
+  return `board:${boardId}`;
+}
+
+function getActiveUsersInRoom(roomName) {
+  if (!activeUsers.has(roomName)) {
+    activeUsers.set(roomName, new Map());
+  }
+  return activeUsers.get(roomName);
+}
+
+function setupBoardRoom(io, socket) {
+
+  // ---- Join / Leave ----
+
+  socket.on('board:join', ({ boardId }, callback) => {
+    try {
+      const board = getBoard(boardId);
+      if (!board) return callback?.({ error: 'Board not found' });
+
+      const collection = getCollection(board.collection_id);
+      if (!collection) return callback?.({ error: 'Collection not found' });
+
+      const member = getCollectionMember(board.collection_id, socket.userId);
+      if (!member && !collection.is_public) return callback?.({ error: 'Access denied' });
+
+      const roomName = getRoomName(boardId);
+
+      // Leave any previous board room
+      for (const room of socket.rooms) {
+        if (room.startsWith('board:') && room !== roomName) {
+          leaveRoom(io, socket, room);
+        }
+      }
+
+      socket.join(roomName);
+      socket.currentBoardId = boardId;
+
+      const roomUsers = getActiveUsersInRoom(roomName);
+      const userInfo = {
+        id: socket.userId,
+        display_name: socket.userDisplayName,
+        email: socket.userEmail,
+        role: member?.role || 'viewer',
+      };
+      roomUsers.set(socket.userId, userInfo);
+
+      socket.to(roomName).emit('user:joined', userInfo);
+
+      const users = Array.from(roomUsers.values());
+      callback?.({ ok: true, users });
+
+      console.log(`[socket] ${socket.userDisplayName} joined ${roomName} (${users.length} users)`);
+    } catch (err) {
+      console.error('[socket] board:join error:', err);
+      callback?.({ error: 'Failed to join board' });
+    }
+  });
+
+  socket.on('board:leave', ({ boardId }, callback) => {
+    const roomName = getRoomName(boardId);
+    leaveRoom(io, socket, roomName);
+    callback?.({ ok: true });
+  });
+
+  // ---- Full scene sync (Excalidraw-style) ----
+
+  socket.on('scene:update', (data) => {
+    if (!socket.currentBoardId) return;
+    const roomName = getRoomName(socket.currentBoardId);
+    socket.to(roomName).emit('scene:update', {
+      ...data,
+      userId: socket.userId,
+    });
+  });
+
+  // ---- Lightweight transform (during drag/resize/rotate) ----
+
+  socket.on('object:transform', (data) => {
+    if (!socket.currentBoardId) return;
+    const roomName = getRoomName(socket.currentBoardId);
+    socket.to(roomName).emit('object:transform', {
+      ...data,
+      userId: socket.userId,
+    });
+  });
+
+  // ---- Cursor movement ----
+
+  socket.on('cursor:move', (data) => {
+    if (!socket.currentBoardId) return;
+    const roomName = getRoomName(socket.currentBoardId);
+    socket.to(roomName).emit('cursor:moved', {
+      ...data,
+      userId: socket.userId,
+      displayName: socket.userDisplayName,
+    });
+  });
+
+  // ---- Disconnect cleanup ----
+
+  socket.on('disconnect', () => {
+    for (const room of socket.rooms) {
+      if (room.startsWith('board:')) {
+        leaveRoom(io, socket, room);
+      }
+    }
+    if (socket.currentBoardId) {
+      const roomName = getRoomName(socket.currentBoardId);
+      leaveRoom(io, socket, roomName);
+    }
+  });
+}
+
+function leaveRoom(io, socket, roomName) {
+  socket.leave(roomName);
+
+  const roomUsers = getActiveUsersInRoom(roomName);
+  roomUsers.delete(socket.userId);
+
+  socket.to(roomName).emit('user:left', {
+    id: socket.userId,
+    display_name: socket.userDisplayName,
+  });
+
+  if (roomUsers.size === 0) {
+    activeUsers.delete(roomName);
+  }
+
+  if (socket.currentBoardId && roomName === getRoomName(socket.currentBoardId)) {
+    socket.currentBoardId = null;
+  }
+
+  console.log(`[socket] ${socket.userDisplayName} left ${roomName}`);
+}
+
+module.exports = { setupBoardRoom };