Glossary: Add `context` to glossary form and change permission check

[Xzonn]

Proposed changes

Add an input box for context to glossary form in the translation UI (#10969), based on NewMonolingualUnitForm:

https://github.com/WeblateOrg/weblate/blob/8f105d79a47b28c333d01d20ff4b4b9f27d8baad/weblate/trans/forms.py#L2375-L2391

I also noticed that there is a significant difference between NewMonolingualUnitForm and NewBilingualSourceUnitForm. Should we unify them?

I also changed the permission check from unit.add to glossary.add. Before this commit, terms can not be directly added to the glossary because of this check:

https://github.com/WeblateOrg/weblate/blob/4774584fd9e6d3795a0c40bb0c3520bf2a21875a/weblate/auth/permissions.py#L273-L274

Checklist

• [x] Lint and unit tests pass locally with my changes.
• [ ] I have added tests that prove my fix is effective or that my feature works.
• [ ] I have added documentation to describe my feature.
• [x] I have squashed my commits into logic units.
• [x] I have described the changes in the commit messages.

Other information

Screenshot

[Xzonn]

I changed TermForm to inherit NewBilingerGlossaryUnitForm in order to avoid the field description and help texts:

Screenshot

The font size for .highlighted-output should be set to 16px, but I'm not sure which CSS file to add to.

[github-actions[bot]]

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 75.00000% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 90.62%. Comparing base (6aee586) to head (994edb7). Report is 1656 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11063      +/-   ##
==========================================
- Coverage   90.82%   90.62%   -0.21%     
==========================================
  Files         554      570      +16     
  Lines       57306    58599    +1293     
  Branches     9122     9373     +251     
==========================================
+ Hits        52046    53103    +1057     
- Misses       3640     3810     +170     
- Partials     1620     1686      +66     

Files	Coverage Δ
weblate/glossary/tests.py	100.00% <ø> (ø)
weblate/glossary/forms.py	74.13% <81.81%> (-1.58%)	:arrow_down:
weblate/trans/forms.py	87.84% <69.23%> (-0.03%)	:arrow_down:

... and 241 files with indirect coverage changes

[nijel]

Merged, thanks for your contribution!