Return per-version filename in fleet_maintained_versions

[cdcme]

Related issue: Resolves #48334

The software title response now returns a per-version filename in fleet_maintained_versions, and the Library version rows render each version's own filename instead of the active installer's. Previously, every cached-version row showed the active installer's filename because the array didn't include one.

Checklist for submitter

• Input data is properly validated, SELECT * is avoided, SQL injection is prevented (using placeholders for values in statements), JS inline code is prevented especially for url redirects, and untrusted data interpolated into shell scripts/commands is validated against shell metacharacters.

Testing

• Added/updated automated tests
• QA'd all new/changed functionality manually

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.45%. Comparing base (d8c4faa) to head (72b2ef3).

Additional details and impacted files

@@                             Coverage Diff                             @@
##           feat/38504-auto-update-pin-rollback-fma   #48335      +/-   ##
===========================================================================
+ Coverage                                    67.36%   67.45%   +0.09%     
===========================================================================
  Files                                         3668     3668              
  Lines                                       232220   232216       -4     
  Branches                                     12401    12402       +1     
===========================================================================
+ Hits                                        156428   156642     +214     
+ Misses                                       61790    61535     -255     
- Partials                                     14002    14039      +37     

Flag	Coverage Δ
backend	68.99% <100.00%> (+0.11%)	⬆️
frontend	59.01% <ø> (+<0.01%)	⬆️

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[jkatz01]

Approving for backend, thanks!