Add zone resizing to graphical editor

Implemented comprehensive zone resizing functionality in the zone editor:

Features:
- Detects when mouse is near zone edges/corners (10px threshold)
- Supports all 8 resize handles: N, S, E, W, NE, NW, SE, SW
- Visual feedback with cyan highlight during resize
- Real-time dimension label updates while resizing
- Enforces minimum zone size (20x20 pixels)
- Constrains resizing to monitor boundaries
- Maintains zone data structure integrity during resize

Implementation details:
- Added state tracking: isResizingZone, resizingZoneIndex, resizeEdge, originalZoneBounds
- New method _findResizeEdge() for edge/corner detection
- Enhanced _onButtonPress() to prioritize resize over move
- Extended _onMotion() with resize delta calculations for all 8 directions
- Updated instruction label to include resize guidance
- Updated TODO.md to mark item #17 as completed

The zone editor now supports create, move, and resize operations with
clear visual feedback for each mode (green=normal, yellow=moving, cyan=resizing).

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

TODO.md

@@ -60,6 +60,18 @@
 - [x] Maintain zone size while moving (only change position)
 - [ ] Snap to grid or guides (future enhancement)
 
+### 17. Resize Zones in Editor ✅ COMPLETED
+**Priority: High**
+- [x] Detect mouse near edges and corners of zones (10px threshold)
+- [x] Allow dragging edges to resize zones horizontally or vertically
+- [x] Allow dragging corners to resize zones diagonally
+- [x] Visual feedback when zone is being resized (cyan highlight)
+- [x] Show dimension label during resize with real-time updates
+- [x] Enforce minimum zone size (20x20 pixels)
+- [x] Constrain resize to monitor bounds
+- [x] Update zone data structure in real-time during resize
+- [x] Support all 8 resize handles (N, S, E, W, NE, NW, SE, SW)
+
 ## Code Quality & Robustness
 
 ### 6. Comprehensive Error Handling