Ensure OAuth expiry is numeric and can be compared

[philippjfr]

Fixes #6895

[codecov]

Codecov Report

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

Project coverage is 82.21%. Comparing base (3697335) to head (2bfe29f).
Report is 5 commits behind head on main.

Files	Patch %	Lines
panel/auth.py	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7191      +/-   ##
==========================================
+ Coverage   72.23%   82.21%   +9.98%     
==========================================
  Files         329      330       +1     
  Lines       49342    49359      +17     
==========================================
+ Hits        35640    40581    +4941     
+ Misses      13702     8778    -4924     

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