fix(frontend): Fix the base URL supplied to the frontend

[kondratovbr]

I've encountered an issue when running behind a reverse proxy. Proxy terminates SSL correctly and provides correct X-Forwarded headers, but URLs generated for the frontend aren't https, so it tries to call the API via http which browsers explicitly forbid and throw an error along the lines of ...was not allowed to display insecure content from http://...

This PR fixes the BASE_URL explicitly used in Vue and the URL in <base> tag which may be used implicitly.

Now the "non-working" APP_URL ENV value actually does something.

[what-the-diff]

PR Summary

• Introduction of a New Function base_url()
  The team has added a new function named base_url() in the app/Helpers.php file. This function is designed to return the base URL of your application, which is essentially the root web address of your site. This could make it easier to manage and reference URLs across the application.

• Modification in <base> Tag in base.blade.php
  The <base> HTML tag inside the resources/views/base.blade.php file has been updated to utilize the newly introduced base_url() function. This means that the base URL for all the relative URLs in the page will now be managed by this function, improving code consistency and maintainability.

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -0.05% ⚠️

Comparison is base (f2aff43) 83.99% compared to head (8bea390) 83.94%.
Report is 2 commits behind head on master.

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Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1706      +/-   ##
============================================
- Coverage     83.99%   83.94%   -0.05%     
  Complexity      643      643              
============================================
  Files           143      143              
  Lines          1737     1738       +1     
============================================
  Hits           1459     1459              
- Misses          278      279       +1     

Files Changed	Coverage Δ
app/Helpers.php	76.47% <0.00%> (-4.78%)	⬇️

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[phanan]

Thanks!

[phanan]

Reverted, as this caused #1732.