TableFormer V1 & V2 mishandling merged rows and columns, irrespective if cell_matching True or False

### Bug
The ScheduleTable.pdf test case attached contains a table with both column and row mergeing. We found no combination of TableTransformer V1 or V2, with or without cell matching that would correctly capture the table structure.

The results are summarized here, with the details in the comments

[ScheduleTable.docx](https://github.com/user-attachments/files/29341249/ScheduleTable.docx)

[ScheduleTable.pdf](https://github.com/user-attachments/files/29341447/ScheduleTable.pdf)

The source PDF document contains the same table as a table strucure and as an image of the table.
The PDF was exported from the attached DOCX
...

### Steps to reproduce
Using the ScheduleTable.pdf as the source document
with the following options:

#pipeline_options.table_structure_options = TableStructureV2Options()
pipeline_options.table_structure_options.mode = TableFormerMode.ACCURATE
pipeline_options.table_structure_options.do_cell_matching = True
pipeline_options.images_scale = 2.0
pipeline_options.generate_picture_images = False
pipeline_options.generate_page_images = True

converter = DocumentConverter( format_options={
InputFormat.PDF: PdfFormatOption(pipeline_options=pipeline_options)
})
conversion= converter.convert(source)
doc: DoclingDocument = conversion.document

Four permutations were tested:

V1 vs V2 and cell_matching True vs. False

The 'output' for each of the test runs show the tables as jpeg, html, and otsl and these are available for each of the 4 permutations if that would help (see comment below)

We understand that the table has a challenging structure!!!
...

### Docling version
docling ==2.107.0
...

### Python version

Python 3.12.6
...

Reproduce the issue with ScheduleTable.pdf using DocumentConverter, PdfFormatOption, TableStructureV2Options, and the four TableFormer V1/V2 and cell-matching permutations described. Compare the generated JPEG, HTML, and OTSL outputs with the source table and review the attached results in the comments. Done means the merged rows and columns are represented correctly across the reported configurations.

Written by the indexing model from the issue text.