Make structure icon recovery state-sourced after runtime renderer disruption

[Copilot]

Description:

I don't have a clean repro for the mid-match structure icon issue yet, so this PR is meant to reduce the chance of structure icons getting lost after a renderer reset.

This also does not address the separate issue where structure icons sometimes fail to show from game start.

This changes structure icon rendering to rebuild from the current game state instead of mostly waiting for future unit updates.

Main changes:

• make StructureIconsLayer.redraw() rebuild structure icons from game.units()
• rebuild the layer again after WebGL context restore
• recalculate structure positions after resize/reset
• clear stale Pixi children before rebuilding
• add focused tests around redraw/rebuild behavior

Please complete the following:

• I have added screenshots for all UI updates
• I process any text displayed to the user through translateText() and I've added it to the en.json file
• I have added relevant tests to the test directory
• I confirm I have thoroughly tested these changes and take full responsibility for any bugs introduced

Please put your Discord username so you can be contacted if a bug or regression is found:

skigim

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Skigim]

Closing this fork-local PR in favor of the upstream PR: openfrontio#3480