Add connected technician tracking to dashboard

- Add ViewerInfo struct to track viewer name and connection time
- Update session manager to track viewers with names
- Update API to return viewer list for each session
- Update dashboard to display "Mike Connected (3 min)" on machine bars
- Update viewer.html to pass viewer_name parameter

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

server/static/viewer.html

@@ -174,6 +174,10 @@
             window.close();
         }
 
+        // Get viewer name from localStorage (same as dashboard)
+        const user = JSON.parse(localStorage.getItem('user') || 'null');
+        const viewerName = user?.name || user?.email || 'Technician';
+
         // State
         let ws = null;
         let canvas = document.getElementById('viewer-canvas');
@@ -593,7 +597,7 @@
 
         function connect() {
             const protocol = window.location.protocol === 'https:' ? 'wss:' : 'ws:';
-            const wsUrl = `${protocol}//${window.location.host}/ws/viewer?session_id=${sessionId}`;
+            const wsUrl = `${protocol}//${window.location.host}/ws/viewer?session_id=${sessionId}&viewer_name=${encodeURIComponent(viewerName)}`;
 
             console.log('Connecting to:', wsUrl);
             updateStatus('connecting', 'Connecting...');