Integrates #1487 - touch events

Need to add:
- Pinch zoom
- Touch-specific handling (some things aren't quite right)

frontend/src/features/canvas/components/IAICanvas.tsx

@@ -149,6 +149,9 @@ const IAICanvas = () => {
           width={stageDimensions.width}
           height={stageDimensions.height}
           scale={{ x: stageScale, y: stageScale }}
+          onTouchStart={handleMouseDown}
+          onTouchMove={handleMouseMove}
+          onTouchEnd={handleMouseUp}
           onMouseDown={handleMouseDown}
           onMouseEnter={handleMouseEnter}
           onMouseLeave={handleMouseOut}

frontend/src/features/canvas/hooks/useCanvasMouseDown.ts

@@ -31,7 +31,7 @@ const useCanvasMouseDown = (stageRef: MutableRefObject<Konva.Stage | null>) => {
   const { tool, isStaging } = useAppSelector(selector);
 
   return useCallback(
-    (e: KonvaEventObject<MouseEvent>) => {
+    (e: KonvaEventObject<MouseEvent | TouchEvent>) => {
       if (!stageRef.current) return;
 
       stageRef.current.container().focus();