Drop local backup

[MateoLostanlen]

We originally added this local backup at the time because our systems were unstable and we lacked data. We did not want to lose a single fire image

Today, it is very rare for a system to be down, and we now have a large amount of data, so we can afford to lose an image from time to time

Moreover, we never actually retrieve this data from the Raspberry Pi. It is simply deleted by the garbage collector. This unnecessarily accelerates the wear of the SD card

let's keep the functionality if needed but turn it off by default

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.54%. Comparing base (c1fdf2a) to head (b1c8c94).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #319      +/-   ##
===========================================
+ Coverage    80.49%   80.54%   +0.04%     
===========================================
  Files            7        7              
  Lines          810      812       +2     
===========================================
+ Hits           652      654       +2     
  Misses         158      158              

Flag	Coverage Δ
unittests	80.54% <100.00%> (+0.04%)	⬆️

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