fix(ui): resolve file-browser license title and ignore invalid selected ids

[vcnainala]

Summary

• Declare the study prop and compute download-terms licenseTitle from project or study so Vue no longer reads an undeclared study in the template.
• Ignore empty or non-numeric selected query params so the file browser does not write selected=undefined into the URL.

Test plan

• Open a public study file browser and confirm the download-terms modal shows the study license title.
• Select a file, then clear/invalid ?selected= and confirm the URL is not updated with undefined.
• php artisan test --filter=FileSystemBrowserLicenseTitleTest

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.25%. Comparing base (8681915) to head (52180fd).

Additional details and impacted files

@@                Coverage Diff                @@
##             development    #1545      +/-   ##
=================================================
- Coverage          80.26%   80.25%   -0.01%     
  Complexity          4481     4481              
=================================================
  Files                293      293              
  Lines              16424    16424              
=================================================
- Hits               13182    13181       -1     
- Misses              3242     3243       +1     

Flag	Coverage Δ
unittests	80.25% <ø> (-0.01%)	⬇️

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