feat: add unique header to dashboard

[wrt95]

Description

• Added unique header to dashboard
• See this PR for video of full implementation

Related Issue(s)

• Create a unique header #11611

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)
• Relevant automated test added (if you find this hard, leave it and we'll help out)

[codecov]

Codecov Report

Attention: Patch coverage is 96.69421% with 4 lines in your changes missing coverage. Please review.

Project coverage is 94.41%. Comparing base (85a8c66) to head (5bfda26).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...ges/PageLayout/DashboardHeader/DashboardHeader.tsx	94.73%	0 Missing and 2 partials ⚠️
frontend/dashboard/testing/mocks.tsx	80.00%	1 Missing ⚠️
...navigation/main-header/ProfileMenu/ProfileMenu.tsx	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13627      +/-   ##
==========================================
+ Coverage   94.38%   94.41%   +0.03%     
==========================================
  Files        1560     1573      +13     
  Lines       21176    21277     +101     
  Branches     2529     2541      +12     
==========================================
+ Hits        19986    20089     +103     
+ Misses        946      943       -3     
- Partials      244      245       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[wrt95]

Moved to block because of this PR.

[framitdavid]

Tested OK on localhost. :)