fix(export): escape non-HTML tags

[MyvTsv]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes !39136
• This PR fixes the behavior of PDF export when content contains non-HTML tags (such as XML or custom tags).

Before this change:
Unknown tags were removed by TCPDF when calling writeHTML().
This made the text unreadable if the content included XML or custom tags.

After this change:
Only basic HTML tags are interpreted and retained.
All other tags are escaped ( → <tag>) to appear as-is in the PDF.
The final rendering preserves the meaning of the text, and normal HTML tags continue to function.

Screenshots (if appropriate):

Knowlegde Base:

PDF File Before Fix:

PDF File After Fix:

[stonebuzz]

Waiting for customer feedback