Ensure existing http auth tokens shown

[hardillb]

fixes #4860

Description

If there existing Instance HTTP Auth tokens, but FlowFuse auth is not enabled, when enabling the tokens were not shown.

Related Issue(s)

#4860

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production

Labels

• Includes a DB migration? -> add the area:migration label

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.70%. Comparing base (12e82ee) to head (02b8856).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4861   +/-   ##
=======================================
  Coverage   78.70%   78.70%           
=======================================
  Files         316      316           
  Lines       15152    15152           
  Branches     3486     3486           
=======================================
  Hits        11925    11925           
  Misses       3227     3227           

Flag	Coverage Δ
backend	78.70% <ø> (ø)

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