[frontend] Text editor improvements (#15392)

[Ludovic Bouges (ludovic)]

Proposed changes

• Introduce Tiptap as a new rich text editor, placed behind a feature flag while keeping CKEditor as the default
• Add support for key formatting features: font size, highlight colors, indentation, checkboxes, page breaks, source mode
• Improve table handling with nested table support, inline width preservation, and a custom legacy table extension
• Improve image handling with figure support and backward compatibility
• Fix various styling issues (paragraphs in tables, blockquote/paragraph spacing, preformatted text, highlight colors)

Related issues

• Fixes Text editor improvements #15392

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case (coverage and e2e)
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

[codecov]

Codecov Report

❌ Patch coverage is 2.96643% with 1243 lines in your changes missing coverage. Please review.
✅ Project coverage is 33.46%. Comparing base (3ba5330) to head (958129a).
⚠️ Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
...rm/opencti-front/src/components/RichTextEditor.tsx	0.75%	393 Missing ⚠️
...ents/richTextEditor/extensions/ImageWithOptions.ts	0.45%	219 Missing ⚠️
...onents/richTextEditor/extensions/TableCellSplit.ts	0.79%	125 Missing ⚠️
.../components/richTextEditor/TiptapEditorToolbar.tsx	4.16%	115 Missing ⚠️
.../src/components/richTextEditor/extensions/Table.ts	1.49%	66 Missing ⚠️
.../src/components/richTextEditor/TableGridPicker.tsx	7.81%	59 Missing ⚠️
...tform/opencti-front/src/components/HtmlDisplay.tsx	0.00%	45 Missing ⚠️
.../components/richTextEditor/extensions/PageBreak.ts	2.77%	35 Missing ⚠️
...ncti-front/src/components/fields/RichTextField.tsx	0.00%	25 Missing ⚠️
...src/components/richTextEditor/TableContextMenu.tsx	8.33%	22 Missing ⚠️
... and 18 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #15370      +/-   ##
==========================================
- Coverage   33.55%   33.46%   -0.09%     
==========================================
  Files        3168     3190      +22     
  Lines      214726   216256    +1530     
  Branches    39469    39863     +394     
==========================================
+ Hits        72057    72376     +319     
- Misses     142669   143880    +1211     

Flag	Coverage Δ
opencti-client-python	45.60% <ø> (ø)
opencti-front	2.94% <2.96%> (-0.01%)	⬇️
opencti-graphql	69.96% <ø> (+0.09%)	⬆️

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