remove image logo alt name to fix gmail email summary

[cstns]

Description

removed logo img alt name so it won't appear in the summary on gmail

Related Issue(s)

closes #4593

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 78.30%. Comparing base (d3e74b4) to head (3127ca7).
Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4595   +/-   ##
=======================================
  Coverage   78.30%   78.30%           
=======================================
  Files         302      302           
  Lines       14360    14360           
  Branches     3265     3265           
=======================================
  Hits        11244    11244           
  Misses       3116     3116           

Flag	Coverage Δ
backend	78.30% <ø> (ø)

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