feat(mobile): add touch gesture support for mobile devices

Added comprehensive touch support for mobile/tablet usage:

Touch Gestures Hook:
- Created useTouchGestures hook for pinch-to-zoom and two-finger pan
- Handles multi-touch events with distance calculation
- Integrated with canvas store for zoom and pan state
- Prevents default touch behaviors (pull-to-refresh, page scroll)

Features:
- Pinch-to-zoom: Two-finger pinch gesture for zoom in/out
- Two-finger pan: Pan canvas with two fingers
- Touch drawing: Single touch works for all drawing tools (pointer events already supported)
- Min/max zoom limits (0.1x - 32x)
- Smooth gesture handling with distance thresholds

UI Improvements:
- Added touch-action: none CSS to prevent default touch behaviors
- Added touch-none Tailwind class for better touch handling
- Canvas container properly handles touch events

Mobile Experience:
- Drawing tools work with single touch
- Zoom/pan gestures feel natural
- No interference with browser touch behaviors
- Optimized for tablets and touch-enabled devices

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

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

hooks/use-touch-gestures.ts

@@ -0,0 +1,152 @@
+import { useEffect, useRef, useCallback } from 'react';
+import { useCanvasStore } from '@/store';
+
+interface TouchGestureOptions {
+  onPinchZoom?: (scale: number, centerX: number, centerY: number) => void;
+  onTwoFingerPan?: (deltaX: number, deltaY: number) => void;
+  minScale?: number;
+  maxScale?: number;
+}
+
+interface TouchPoint {
+  x: number;
+  y: number;
+}
+
+/**
+ * Hook to handle touch gestures (pinch-to-zoom, two-finger pan)
+ */
+export function useTouchGestures(
+  elementRef: React.RefObject<HTMLElement | null>,
+  options: TouchGestureOptions = {}
+) {
+  const {
+    onPinchZoom,
+    onTwoFingerPan,
+    minScale = 0.1,
+    maxScale = 32,
+  } = options;
+
+  const { setZoom, setPanOffset, zoom } = useCanvasStore();
+
+  const lastTouches = useRef<TouchPoint[]>([]);
+  const initialDistance = useRef<number>(0);
+  const initialZoom = useRef<number>(1);
+
+  const getTouchPoints = useCallback((touches: TouchList): TouchPoint[] => {
+    const points: TouchPoint[] = [];
+    for (let i = 0; i < touches.length; i++) {
+      points.push({
+        x: touches[i].clientX,
+        y: touches[i].clientY,
+      });
+    }
+    return points;
+  }, []);
+
+  const getDistance = useCallback((p1: TouchPoint, p2: TouchPoint): number => {
+    const dx = p2.x - p1.x;
+    const dy = p2.y - p1.y;
+    return Math.sqrt(dx * dx + dy * dy);
+  }, []);
+
+  const getCenter = useCallback((p1: TouchPoint, p2: TouchPoint): TouchPoint => {
+    return {
+      x: (p1.x + p2.x) / 2,
+      y: (p1.y + p2.y) / 2,
+    };
+  }, []);
+
+  const handleTouchStart = useCallback(
+    (e: TouchEvent) => {
+      if (e.touches.length === 2) {
+        // Two-finger gesture starting
+        e.preventDefault();
+
+        const touches = getTouchPoints(e.touches);
+        lastTouches.current = touches;
+        initialDistance.current = getDistance(touches[0], touches[1]);
+        initialZoom.current = zoom;
+      }
+    },
+    [getTouchPoints, getDistance, zoom]
+  );
+
+  const handleTouchMove = useCallback(
+    (e: TouchEvent) => {
+      if (e.touches.length === 2) {
+        // Pinch-to-zoom and two-finger pan
+        e.preventDefault();
+
+        const touches = getTouchPoints(e.touches);
+
+        if (lastTouches.current.length === 2) {
+          // Calculate zoom
+          const currentDistance = getDistance(touches[0], touches[1]);
+          const scaleChange = currentDistance / initialDistance.current;
+          const newZoom = Math.max(
+            minScale,
+            Math.min(maxScale, initialZoom.current * scaleChange)
+          );
+
+          // Get center point for zoom
+          const center = getCenter(touches[0], touches[1]);
+
+          if (onPinchZoom) {
+            onPinchZoom(newZoom, center.x, center.y);
+          } else {
+            setZoom(newZoom);
+          }
+
+          // Calculate pan
+          const lastCenter = getCenter(lastTouches.current[0], lastTouches.current[1]);
+          const deltaX = center.x - lastCenter.x;
+          const deltaY = center.y - lastCenter.y;
+
+          if (onTwoFingerPan && (Math.abs(deltaX) > 1 || Math.abs(deltaY) > 1)) {
+            onTwoFingerPan(deltaX, deltaY);
+          } else if (Math.abs(deltaX) > 1 || Math.abs(deltaY) > 1) {
+            const { offsetX, offsetY } = useCanvasStore.getState();
+            setPanOffset(offsetX + deltaX, offsetY + deltaY);
+          }
+        }
+
+        lastTouches.current = touches;
+      }
+    },
+    [
+      getTouchPoints,
+      getDistance,
+      getCenter,
+      minScale,
+      maxScale,
+      onPinchZoom,
+      onTwoFingerPan,
+      setZoom,
+      setPanOffset,
+    ]
+  );
+
+  const handleTouchEnd = useCallback(() => {
+    lastTouches.current = [];
+    initialDistance.current = 0;
+  }, []);
+
+  useEffect(() => {
+    const element = elementRef.current;
+    if (!element) return;
+
+    // Add touch event listeners with passive: false to allow preventDefault
+    element.addEventListener('touchstart', handleTouchStart, { passive: false });
+    element.addEventListener('touchmove', handleTouchMove, { passive: false });
+    element.addEventListener('touchend', handleTouchEnd);
+    element.addEventListener('touchcancel', handleTouchEnd);
+
+    return () => {
+      element.removeEventListener('touchstart', handleTouchStart);
+      element.removeEventListener('touchmove', handleTouchMove);
+      element.removeEventListener('touchend', handleTouchEnd);
+      element.removeEventListener('touchcancel', handleTouchEnd);
+    };
+  }, [elementRef, handleTouchStart, handleTouchMove, handleTouchEnd]);
+}