fix: тема доски синхронизируется между учителем и учениками в реальном времени

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/controllers/classroomController.js

@@ -22,6 +22,7 @@ const GUEST_EVENTS = new Set([
   'classroom_stroke_updated', 'classroom_page_added', 'classroom_page_changed',
   'classroom_template_changed', 'classroom_page_cleared', 'classroom_page_renamed',
   'classroom_page_duplicated', 'classroom_page_deleted', 'classroom_ended',
+  'classroom_board_theme',
 ]);
 
 /* ── Helper: broadcast to all session participants ─────────────────────── */
@@ -490,6 +491,21 @@ function updatePageTemplate(req, res) {
   res.json({ ok: true, template });
 }
 
+/* PATCH /api/classroom/:id/board-theme — change board theme and broadcast to all */
+function updateBoardTheme(req, res) {
+  const sessionId = Number(req.params.id);
+  const VALID_THEMES = new Set(['chalkboard', 'blackboard', 'whiteboard', 'dark', 'grid', 'dots']);
+  const { theme } = req.body;
+  if (!theme || !VALID_THEMES.has(theme)) return res.status(400).json({ error: 'invalid theme' });
+  const session = db.prepare(`SELECT * FROM classroom_sessions WHERE id=? AND status='active'`).get(sessionId);
+  if (!session) return res.status(404).json({ error: 'Сессия не активна' });
+  if (session.teacher_id !== req.user.id && req.user.role !== 'admin')
+    return res.status(403).json({ error: 'Нет доступа' });
+  db.prepare('UPDATE classroom_sessions SET board_theme=? WHERE id=?').run(theme, sessionId);
+  emitToSession(sessionId, { type: 'classroom_board_theme', sessionId, theme });
+  res.json({ ok: true, theme });
+}
+
 /* POST /api/classroom/:id/hand — raise hand */
 function raiseHand(req, res) {
   const sessionId = Number(req.params.id);
@@ -1521,6 +1537,7 @@ module.exports = {
   addPage,
   changePage,
   updatePageTemplate,
+  updateBoardTheme,
   getPages,
   renamePage,
   duplicatePage,