feat(frontend): implement via mode for setting destinations and add MapNode disableNavigate prop

frontend/src/components/SystemContextMenu.tsx

@@ -8,7 +8,7 @@ interface SystemContextMenuProps {
   onRename: (newName: string) => void;
   onDelete: (system: System) => void;
   onClearConnections: (system: System) => void;
-  onSetDestination: (systemName: string, viaMode: boolean) => void;
+  onSetDestination?: (systemName: string, viaMode: boolean) => void;
   onClose: () => void;
 }
 
@@ -28,6 +28,16 @@ export const SystemContextMenu = ({ x, y, system, onRename, onDelete, onClearCon
     setIsRenaming(false);
   };
 
+  const handleSetDestinationClick = (e: React.MouseEvent) => {
+    const via = !!e.shiftKey;
+    if (typeof onSetDestination === 'function') {
+      onSetDestination(system.solarSystemName, via);
+    } else {
+      console.error('onSetDestination not provided');
+    }
+    onClose();
+  };
+
   return (
     <div
       ref={menuRef}
@@ -85,7 +95,7 @@ export const SystemContextMenu = ({ x, y, system, onRename, onDelete, onClearCon
           </button>
           <div className="h-px bg-slate-700 my-1" />
           <button
-            onClick={(e) => { onSetDestination(system.solarSystemName, e.shiftKey); onClose(); }}
+            onClick={handleSetDestinationClick}
             className="w-full px-3 py-1 text-left text-emerald-400 hover:bg-slate-700 rounded text-sm"
             title="Shift-click to enter via mode and append waypoints"
           >