fix(IE.Excel): 修复 P0-1 DoAdjustDrawings ship-blocker 及配套清理

P0-1 [高] DoAdjustDrawings = false 恢复无 try/finally
  位置: ExportHelper.AddPictures line 932-1014
  风险: 任一处抛未捕获异常时, package.DoAdjustDrawings 永久卡在 false,
        后续用户代码 Row.Height = X / Column.Width = X / Column.Hidden = X
        静默失效 (setter 走 _worksheet._package.DoAdjustDrawings 分支)
  修复: 用 try/finally 包裹原 938-1010 整段, finally 恢复 prevDoAdjust
  验证: 33/33 image-related 测试通过 (含 500/1000/2000 行压力);
        319/319 全套测试通过

P1-1 [中] Preallocate 估算过乘
  旧: imageUrls.Count * rowCount * imageColCount (3-way 过乘)
  新: rowCount * imageColCount (精确值)
  实际 drawing 数 = rowCount * imageColCount, imageUrls.Count 是 unique URLs

P1-2 [低] _doNotAdjust 收紧访问
  旧: protected internal (允许跨 assembly 子类访问)
  新: internal (仅同 assembly, ExcelPicture 与基类同 assembly 仍可访问)
  影响: 0 (vendored EPPlus 不暴露给外部继承)

参考: .claude/plans/abstract-gathering-raven.md (P0-1, P1-1, P1-2)

Author: hueifeng

src/EPPlus/EPPlus/Drawing/ExcelDrawingBase.cs

@@ -184,7 +184,7 @@ public int RowOff
         public const int EMU_PER_PIXEL = 9525;
         protected internal int _width = int.MinValue, _height = int.MinValue, _top = int.MinValue, _left = int.MinValue;
         // Subclasses (e.g. ExcelPicture ctor) set this to skip GetPositionSize side effects.
-        protected internal bool _doNotAdjust = false;
+        internal bool _doNotAdjust = false;
         internal ExcelDrawing(ExcelDrawings drawings, XmlNode node, string nameXPath) :
             base(drawings.NameSpaceManager, node)
         {

src/Magicodes.ExporterAndImporter.Excel/Utility/ExportHelper.cs

@@ -926,12 +926,16 @@ protected void AddPictures(int rowCount)
                 if (ExporterHeaderList[c].ExportImageFieldAttribute != null)
                     imageColCount++;
             }
-            CurrentExcelWorksheet.Drawings.Preallocate(imageUrls.Count * rowCount * Math.Max(imageColCount, 1));
+            CurrentExcelWorksheet.Drawings.Preallocate(rowCount * Math.Max(imageColCount, 1));
 
             // 关闭 Row.Height 触发的 drawings 重算(EditAs=OneCell 不依赖 row height 重定位)
+            // 必须用 try/finally 保证 flag 恢复,否则任一处抛未捕获异常都会让 flag 卡在 false,
+            // 后续用户对 Row.Height / Column.Width / Column.Hidden 的 setter 静默失效.
             var package = CurrentExcelPackage;
             var prevDoAdjust = package.DoAdjustDrawings;
             package.DoAdjustDrawings = false;
+            try
+            {
 
             // 并行加载图片
             var imageCache = new System.Collections.Concurrent.ConcurrentDictionary<string, (byte[] bytes, Magicodes.IE.Excel.Images.ImageExtensions.ImageInfo meta)>();
@@ -1007,7 +1011,11 @@ protected void AddPictures(int rowCount)
                     }
                 }
             }
-            package.DoAdjustDrawings = prevDoAdjust;
+            }
+            finally
+            {
+                package.DoAdjustDrawings = prevDoAdjust;
+            }
         }
 
         internal static void AddImage(int rowIndex, int colIndex, ExcelPicture picture, int yOffset, int xOffset)