Pretty print update_interval in preferences page

[hmpf]

Scope and purpose

Fixes #1383. Depends on #1385.

Contributor Checklist

Every pull request should have this checklist filled out, no matter how small it is. More information about contributing to Argus can be found in the Development docs.

• [ ] Added a changelog fragment for towncrier
• [ ] Added/amended tests for new/changed code
• [ ] Added/changed documentation
• [x] Linted/formatted the code with ruff and djLint, easiest by using pre-commit
• [x] The first line of the commit message continues the sentence "If applied, this commit will ...", starts with a capital letter, does not end with punctuation and is 50 characters or less long. See our how-to
• [ ] If applicable: Created new issues if this PR does not fix the issue completely/there is further work to be done
• [ ] If this results in changes in the UI: Added screenshots of the before and after

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov-commenter]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 79.46%. Comparing base (146bfa2) to head (d3935cb). :warning: Report is 33 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1386      +/-   ##
==========================================
- Coverage   79.48%   79.46%   -0.03%     
==========================================
  Files         121      121              
  Lines        5415     5424       +9     
==========================================
+ Hits         4304     4310       +6     
- Misses       1111     1114       +3     

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[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud