chore(addons): fix bulk edit form construction

[nijel]

Proposed changes

Correctly use project scoping when available, see #12957

Checklist

• 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.
• I have squashed my commits into logic units.
• I have described the changes in the commit messages.

Other information

[codecov]

Codecov Report

Attention: Patch coverage is 77.77778% with 2 lines in your changes missing coverage. Please review.

Project coverage is 91.10%. Comparing base (3df5a7c) to head (8ebeda1).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
weblate/addons/forms.py	75.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12961      +/-   ##
==========================================
- Coverage   91.11%   91.10%   -0.01%     
==========================================
  Files         598      598              
  Lines       61433    61439       +6     
  Branches     6368     6370       +2     
==========================================
+ Hits        55972    55976       +4     
- Misses       3798     3799       +1     
- Partials     1663     1664       +1     

Files with missing lines	Coverage Δ
weblate/trans/forms.py	89.90% <100.00%> (ø)
weblate/addons/forms.py	93.66% <75.00%> (-0.76%)	⬇️