Fix 404 for packages in FlowFuse expert due to wrong url pattern

[dimitrieh]

Description

Related Issue(s)

Follow up from #6310

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
• Link to Changelog Entry PR, or note why one is not needed.

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 76.22%. Comparing base (84877e3) to head (4434b70).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6332   +/-   ##
=======================================
  Coverage   76.22%   76.22%           
=======================================
  Files         393      393           
  Lines       19777    19777           
  Branches     4741     4741           
=======================================
  Hits        15075    15075           
  Misses       4702     4702           

Flag	Coverage Δ
backend	76.22% <ø> (ø)

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