[FIX] 47755: Including images with drag-and-drop without specifying image size leads to missing editor buttons

[chfsx]

Summary

Drag-dropped images without explicit dimensions caused TinyMCE init to fail on edit of forum posts (toolbar buttons missing).

The forum does not load the image plugin and has no ILIAS-mob integration in the editor toolbar — drag-drop bypasses this by embedding images as data: URIs. On reload, TinyMCE's async image-dimension detection on dimensionless data-URI images breaks the toolbar render.

Fix

In tpl.tinymce_frm_post.js:

• image_dimensions: false — skip async dimension detection (fixes existing posts so they become editable again).
• image_caption: false — no figure-wrapping (consistent with no image plugin loaded).
• paste_data_images: false and images_dataimg_filter: () => false — prevent paste/drag-drop from embedding new data-URI images.

Only tpl.tinymce_frm_post.js is touched — other TinyMCE usages (Wiki, Test, Cert, …) use tpl.tinymce.js and are not affected.

Mantis: https://mantis.ilias.de/view.php?id=47755

Test plan

• Open a forum post that contains a drag-drop image without dimensions → editor loads with toolbar.
• Create a new forum post and try drag-drop / paste of an image → image is not embedded as data URI.
• Other components using TinyMCE (wiki, test, cert) → unchanged behaviour.

[chfsx]

Should be picked to trunk and release_10 as well