Add flowfuse.com to the list of places allowed to load images from

[hardillb]

Description

This is CSP update to remove one more warning and get closer to enforcing, not just reporting.

The sign-up page on FF Cloud loads image from the website.

Related Issue(s)

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 79.28%. Comparing base (78ee033) to head (9c68ae2).
Report is 21 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3924   +/-   ##
=======================================
  Coverage   79.28%   79.28%           
=======================================
  Files         281      281           
  Lines       12755    12755           
  Branches     2844     2844           
=======================================
  Hits        10113    10113           
  Misses       2642     2642           

Flag	Coverage Δ
backend	79.28% <ø> (ø)

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[knolleary]

Approved, although this is ff cloud specific, so Ideally would be passed in via the config, rather than hardcoded.