feat(annotations): comments, threads, voting system with review mode

Backend:
- comment_threads + comments + object_votes tables with indexes
- Thread/comment CRUD endpoints with socket broadcast
- Vote toggle endpoint with socket broadcast

Frontend:
- AnnotationStore for reactive thread/comment/vote state
- FeedbackPanel with thread list, expanded view, replies, filtering
- Vote toggle buttons in panel
- PinOverlay for canvas pin markers + vote badges
- Review Mode toggle in toolbar (comment bubble icon)
- Jump-to-object from thread view
- Orphaned thread detection for deleted objects
- New comment creation from panel when object selected
- Socket event wiring for real-time sync

backend/server.js

@@ -100,6 +100,8 @@ const boardRoutes = require('./routes/boards');
 const uploadRoutes = require('./routes/upload');
 const adminRoutes = require('./routes/admin');
 const mmBridgeRoutes = require('./routes/mattermost-bridge');
+const threadRoutes = require('./routes/threads');
+const voteRoutes = require('./routes/votes');
 
 app.use('/api/auth', authRoutes);
 app.use('/api/collections', collectionRoutes);
@@ -107,6 +109,8 @@ app.use('/api/boards', boardRoutes);
 app.use('/api/upload', uploadRoutes);
 app.use('/api/admin', adminRoutes);
 app.use('/api/boards', mmBridgeRoutes);
+app.use('/api/boards', threadRoutes);
+app.use('/api/boards', voteRoutes);
 
 // Public shared collection route (no auth required)
 app.get('/api/c/:shareToken', (req, res) => {
@@ -151,6 +155,7 @@ const server = http.createServer(app);
 
 const { setupSocket } = require('./socket');
 const io = setupSocket(server);
+app.set('io', io);
 
 // ---- Initialize services and start ----
 async function start() {