storage: Adjust content types for version downloads archive files

[Turbo87]

Otherwise the index.html is served with Content-Type: binary/octet-stream and the browser shows a download dialog...

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 89.14%. Comparing base (403e7a2) to head (b2cbfec).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/storage.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9295      +/-   ##
==========================================
- Coverage   89.15%   89.14%   -0.02%     
==========================================
  Files         283      283              
  Lines       28817    28821       +4     
==========================================
- Hits        25693    25692       -1     
- Misses       3124     3129       +5     

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