controllers/user/update: Migrate to diesel-async queries

[Turbo87]

less spawn_blocking(), more better!

[codecov]

Codecov Report

Attention: Patch coverage is 98.38710% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.17%. Comparing base (2f4ed8a) to head (b3e73fc).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
src/controllers/user/update.rs	98.03%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9966   +/-   ##
=======================================
  Coverage   89.17%   89.17%           
=======================================
  Files         292      292           
  Lines       30380    30388    +8     
=======================================
+ Hits        27092    27100    +8     
  Misses       3288     3288           

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