fix: eliminate multi-save in batch Add and DeleteAsync(TEntityId)

- Add(TEntity[]) now passes save:false in the loop and calls SaveChanges once at the end
- DeleteAsync(TEntityId) now calls DoRemove directly instead of Delete(TEntityId) to avoid the double-save from the sync overload chain

Ref: #IT-631

HrynCo.DAL.EF/Core/BaseEfRepository.cs

@@ -40,7 +40,12 @@ public abstract class BaseEfRepository<TDbContext, TEntity, TEntityId> :
     {
         foreach (TEntity entity in entities)
         {
-            Add(entity, save);
+            Add(entity, save: false);
+        }
+
+        if (save)
+        {
+            DbContext.SaveChanges();
         }
     }
 
@@ -84,7 +89,11 @@ public abstract class BaseEfRepository<TDbContext, TEntity, TEntityId> :
 
     public async Task DeleteAsync(TEntityId id)
     {
-        Delete(id);
+        TEntity? entity = GetById(id);
+        if (entity != null)
+        {
+            DoRemove(entity);
+        }
         await DbContext.SaveChangesAsync();
     }