Authentication UX and middleware routing

[cstns]

Description

Related Issue(s)

fixes #3849

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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 79.22%. Comparing base (470c42e) to head (6d40f5f). Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3856   +/-   ##
=======================================
  Coverage   79.22%   79.22%           
=======================================
  Files         281      281           
  Lines       12660    12660           
  Branches     2813     2813           
=======================================
  Hits        10030    10030           
  Misses       2630     2630           

Flag	Coverage Δ
backend	79.22% <ø> (ø)

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[cstns]

will be taken into consideration on a bigger overhaul of UI Architecture review