Hide login button when logged out

[Xpirix]

• This is for the following issue: #318
• Please check my comment on the issue: https://github.com/qgis/QGIS-Django/issues/318#issuecomment-1836072624
• Please find below a screenshot of the web site when the user is logged out:

[codecov-commenter]

Codecov Report

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

Comparison is base (b661773) 32.51% compared to head (77a0bf5) 32.51%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #324 +/- ## ======================================= Coverage 32.51% 32.51% ======================================= Files 71 71 Lines 4217 4217 ======================================= Hits 1371 1371 Misses 2846 2846 ```

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[timlinux]

Perfect thanks @Xpirix