Ensure password reset tokens are cleared on use

[knolleary]

Description

This ensures a user can only have a single active password reset token at any one time - and that the token is disposed of at the right times.

Fixes:

• https://github.com/FlowFuse/security/issues/43
• https://github.com/FlowFuse/security/issues/46
• https://github.com/FlowFuse/security/issues/61

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c64aa28) 40.90% compared to head (36da917) 40.98%.
Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3321      +/-   ##
==========================================
+ Coverage   40.90%   40.98%   +0.08%     
==========================================
  Files         605      605              
  Lines       22638    22731      +93     
  Branches     5438     5473      +35     
==========================================
+ Hits         9260     9317      +57     
- Misses      13378    13414      +36     

Flag	Coverage Δ
backend	77.68% <100.00%> (+0.05%)	⬆️
frontend	2.05% <0.00%> (+<0.01%)	⬆️

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