fix: Correct background grid rendering at high zoom levels

- Fix grid line coordinate transformation (world to screen)
- Properly align grid with zoom and pan transformations
- Calculate grid start position at GRID_SIZE multiples
- Draw grid lines across entire visible canvas area
- Ensure grid lines render completely regardless of zoom level
- Grid now displays consistently at all zoom magnifications

Fixes: Grid no longer disappears or renders incompletely when zoomed in

🤖 Generated with Claude Code

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

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

@@ -72,20 +72,31 @@ namespace AGVNavigationCore.Controls
 
             if (gridSize < 5) return; // 너무 작으면 그리지 않음
 
-            for (int x = bounds.Left; x < bounds.Right; x += GRID_SIZE)
+            // 그리드 시작 위치 (월드 좌표에서 GRID_SIZE의 배수 찾기)
+            int startX = (bounds.Left / GRID_SIZE) * GRID_SIZE;
+            int startY = (bounds.Top / GRID_SIZE) * GRID_SIZE;
+
+            // 월드 좌표로 그리드 라인 계산
+            for (int x = startX; x <= bounds.Right; x += GRID_SIZE)
             {
+                // 월드 좌표를 스크린 좌표로 변환
+                int screenX = x * (int)_zoomFactor + _panOffset.X;
+
                 if (x % (GRID_SIZE * 5) == 0)
-                    g.DrawLine(new Pen(Color.Gray, 1), x, bounds.Top, x, bounds.Bottom);
+                    g.DrawLine(new Pen(Color.Gray, 1), screenX, 0, screenX, Height);
                 else
-                    g.DrawLine(_gridPen, x, bounds.Top, x, bounds.Bottom);
+                    g.DrawLine(_gridPen, screenX, 0, screenX, Height);
             }
 
-            for (int y = bounds.Top; y < bounds.Bottom; y += GRID_SIZE)
+            for (int y = startY; y <= bounds.Bottom; y += GRID_SIZE)
             {
+                // 월드 좌표를 스크린 좌표로 변환
+                int screenY = y * (int)_zoomFactor + _panOffset.Y;
+
                 if (y % (GRID_SIZE * 5) == 0)
-                    g.DrawLine(new Pen(Color.Gray, 1), bounds.Left, y, bounds.Right, y);
+                    g.DrawLine(new Pen(Color.Gray, 1), 0, screenY, Width, screenY);
                 else
-                    g.DrawLine(_gridPen, bounds.Left, y, bounds.Right, y);
+                    g.DrawLine(_gridPen, 0, screenY, Width, screenY);
             }
         }