Prevent isAdminMode from becoming undefined and ensure false is stored correctly

[joshdimanteto]

Description

This PR fixes an issue where isAdminMode could become undefined after calling setAuthorisation, causing the authorisation listener middleware to attempt storing undefined into local storage.

Key Fixes:

• setAuthorisation now guarantees isAdminMode is always a boolean.
• Prevents accidental writes of undefined to the storage layer.

Restores intended behaviour:

• isAdminMode persists as true or false
• Non‑admin users always reset to false
• Admin users retain their current mode unless explicitly changed

Testing instructions

Add a set up instructions describing how the reviewer should test the code

• Review code
• Check Actions build
• Review changes to test coverage
• Admin login retains correct isAdminMode state
• Non-admin login clears admin mode
• Middleware no longer writes undefined to storage
• Hydration logic works correctly for true/false values

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 92.83%. Comparing base (686a86b) to head (8eaf626).

Files with missing lines	Patch %	Lines
src/App.tsx	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1738      +/-   ##
===========================================
- Coverage    92.98%   92.83%   -0.15%     
===========================================
  Files           13       13              
  Lines          627      628       +1     
  Branches       195      193       -2     
===========================================
  Hits           583      583              
- Misses          44       45       +1     

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[joelvdavies]

In the testing instructions you say Admin login retains correct isAdminMode state - If I log out as admin then log back in then it gets reset, so that isnt met. I believe because it deletes it on logout. I checked adding the local storage item and then logging in as a non admin and it did clear it so that way round worked as I would hope.

[joshdimanteto]

In the testing instructions you say Admin login retains correct isAdminMode state - If I log out as admin then log back in then it gets reset, so that isnt met. I believe because it deletes it on logout. I checked adding the local storage item and then logging in as a non admin and it did clear it so that way round worked as I would hope.

This should be fixed now, Also this pr need to get merged in before #1717 as it fixes a bug i found