fix: Asset upload dialog

[Steve-Mcl]

closes #4456
closes #4458

Description

Fixes asset upload

• clear 5mb warning when selecting file < 5mb
• clear input value to permit same file selection

Related Issue(s)

#4456
#4458

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production

Labels

• Includes a DB migration? -> add the area:migration label

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.13%. Comparing base (d2c80ee) to head (8cff2c2).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4465   +/-   ##
=======================================
  Coverage   78.13%   78.13%           
=======================================
  Files         296      296           
  Lines       14119    14119           
  Branches     3189     3189           
=======================================
  Hits        11032    11032           
  Misses       3087     3087           

Flag	Coverage Δ
backend	78.13% <ø> (ø)

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