feat: Add middle mouse button panning support

- Support middle mouse button (wheel) for map panning alongside left button
- Middle button drag always enables panning regardless of edit mode
- Change cursor to hand icon during middle button panning for clarity
- Left button panning remains unchanged (mode-dependent behavior preserved)

🤖 Generated with Claude Code

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

Cs_HMI/AGVLogic/AGVNavigationCore/Controls/UnifiedAGVCanvas.Mouse.cs

@@ -76,11 +76,18 @@ namespace AGVNavigationCore.Controls
                     }
                 }
 
-                // 팬 시작 (우클릭 또는 중간버튼)
+                // 팬 시작 (좌클릭 - 모드에 따라)
                 _isPanning = true;
                 _lastMousePosition = e.Location;
                 Cursor = Cursors.SizeAll;
             }
+            else if (e.Button == MouseButtons.Middle)
+            {
+                // 중간 버튼: 항상 팬 (어떤 모드든 상관없이)
+                _isPanning = true;
+                _lastMousePosition = e.Location;
+                Cursor = Cursors.Hand;
+            }
             else if (e.Button == MouseButtons.Right)
             {
                 // 컨텍스트 메뉴 (편집 모드에서만)
@@ -166,6 +173,15 @@ namespace AGVNavigationCore.Controls
                     Cursor = Cursors.Default;
                 }
             }
+            else if (e.Button == MouseButtons.Middle)
+            {
+                // 중간 버튼 드래그 종료
+                if (_isPanning)
+                {
+                    _isPanning = false;
+                    Cursor = Cursors.Default;
+                }
+            }
         }
 
         private void UnifiedAGVCanvas_MouseWheel(object sender, MouseEventArgs e)