v1.2.0: 重构为插件+独立Manager架构，横版UI，精确保留文本框边距的文档转换

Manager/Services/IConversionService.cs

@@ -0,0 +1,11 @@
+using System.Threading.Tasks;
+
+namespace BetterSeewo.Manager.Services
+{
+    public interface IConversionService
+    {
+        Task<string> ConvertPptxToEnbxAsync(string pptxPath);
+        Task<string> ConvertEnbxToPptxAsync(string enbxPath);
+        Task FixConversionErrorsAsync();
+    }
+}