refactor: remove voting system, add author colors + pin numbering

- Remove votes backend (route, db functions, server mount)
- Remove votes frontend (store, socket, PinOverlay badges, FeedbackPanel UI)
- Add authorColors utility (8-color palette, deterministic hash)
- Add getPinNumber() to annotationStore
- Fix JWT to include username/display_name
- Add resolveAuthorName DB fallback for old tokens

backend/server.js

@@ -101,7 +101,6 @@ 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);
@@ -110,7 +109,6 @@ 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) => {