Remove admin site "read only" warnings

[Andrew-Dickinson]

Draft so I don't accidentally merge it too early

[codecov[bot]]

Codecov Report

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

Project coverage is 94.03%. Comparing base (3e0a0e3) to head (7e88d7e).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #635 +/- ## ======================================= Coverage 94.03% 94.03% ======================================= Files 75 75 Lines 3086 3086 ======================================= Hits 2902 2902 Misses 184 184 ```

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[Andrew-Dickinson]

Also makes the map UI "full bleed" by removing the 5px gutters