[5637] Upgrade hericons to v 2.1.5

[n-lark]

Description

See details here.

Related Issue(s)

Resolves #5637

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 76.61%. Comparing base (7f9c612) to head (2b9a584).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7308   +/-   ##
=======================================
  Coverage   76.61%   76.61%           
=======================================
  Files         405      405           
  Lines       20602    20602           
  Branches     4986     4986           
=======================================
  Hits        15784    15784           
  Misses       4818     4818           

Flag	Coverage Δ
backend	76.61% <ø> (ø)

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[n-lark]

So, the old code lazy-loaded each icon. Heroicons v2's exports field broke that, and …/esm/${name}.js didn't work either.

Both tiles (this and BlueprintTileSmall.vue) now lazy-load the whole outline namespace as one dynamic import, webpack splits it into its own chunk, so the ~20 KB loads on demand instead of inflating main.js. loadOutlineIcons is at module scope so all tiles share one fetch. Tried a few different things here lmk if there is a better solution.