FRE-603: Fix code review blockers (memory leak + auth security)

- Fixed memory leak in PresenceManager: event handlers now use bound methods
  so they can be properly removed in shutdown()
- Removed auth token from URL query parameters (security: prevents token leakage
  to server logs and browser history)
- Fixed TypeScript errors: corrected WebsocketProvider import, removed unsupported
  send() calls, fixed type mismatches in presence callbacks
- All collaboration module files now type-check successfully

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/lib/collaboration/websocket-connection.ts

@@ -64,18 +64,14 @@ export class WebSocketConnection implements WebSocketConnectionWithPresence {
       // Create or use provided Yjs doc
       const ydoc = this.options.doc || new Y.Doc();
       
-      // Prepare auth params (y-websocket uses query params for auth)
-      const params: Record<string, string> = {
-        token: this.options.authToken,
-      };
-      
+      // Create provider without auth token in URL (security: tokens in query params leak to logs)
       this.provider = new WebsocketProvider(
         this.options.serverUrl,
         this.options.documentName,
         ydoc,
         {
           connect: true,
-          params,
+          // Don't pass token in URL - send via awareness after connection
           maxBackoffTime: this.options.maxReconnectInterval || 30000,
         }
       );
@@ -88,6 +84,8 @@ export class WebSocketConnection implements WebSocketConnectionWithPresence {
         if (newStatus === 'connected') {
           this.reconnectAttempts = 0;
           this.currentReconnectInterval = this.options.reconnectInterval || 1000;
+          // Send auth token via awareness state after connection (secure: not in URL logs)
+          this.sendAuthToken();
         }
       });
 
@@ -189,6 +187,25 @@ export class WebSocketConnection implements WebSocketConnectionWithPresence {
     }, delay);
   }
 
+  /**
+   * Send auth token via awareness state after connection
+   * Security: Token not exposed in URL/logs, only sent over secure WebSocket
+   */
+  private sendAuthToken(): void {
+    if (!this.provider || !this.provider.awareness) {
+      console.error('[WebSocketConnection] Cannot send auth token: provider not ready');
+      return;
+    }
+    
+    // Store token in awareness state (sent to server, not in URL)
+    this.provider.awareness.setLocalStateField('auth', {
+      token: this.options.authToken,
+      timestamp: Date.now(),
+    });
+    
+    console.log('[WebSocketConnection] Auth token sent via awareness state');
+  }
+
   /**
    * Get the presence manager instance
    */