feat(frontend): Virtual Environments: Show loading spinner while system packages resolve

[SarahAsad23]

What changes were proposed in this PR?

PR #5613 removed the system-requirements-lock.txt file which changes how system packages are loaded. Previously, the package list was available immediately from the lock file. With the new approach, the system package set is generated on demand by creating a temporary environment, installing the requirements, and running pip freeze, which introduces a noticeable delay on the initial load.

The PR introduces new UI changes to handle this new loading state and provide feedback to the user while the system packages are being resolved by adding a loading spinner.

Any related issues, documentation, discussions?

Related PR: #5613.

How was this PR tested?

Tested manually.

Was this PR authored or co-authored using generative AI tooling?

Co-authored using: Claude Code

[github-actions]

👋 Thanks for opening this pull request, @SarahAsad23!

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 5.55556% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 52.50%. Comparing base (73c76f5) to head (6838873).

Files with missing lines	Patch %	Lines
...wer-button/computing-unit-selection.component.html	0.00%	14 Missing ⚠️
...power-button/computing-unit-selection.component.ts	25.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5644      +/-   ##
============================================
- Coverage     52.96%   52.50%   -0.46%     
+ Complexity     2522     2478      -44     
============================================
  Files          1075     1074       -1     
  Lines         41743    41584     -159     
  Branches       4513     4489      -24     
============================================
- Hits          22109    21835     -274     
- Misses        18329    18458     +129     
+ Partials       1305     1291      -14     

Flag	Coverage Δ		*Carryforward flag
access-control-service	64.61% <ø> (-6.82%)	⬇️	Carriedforward from cd60535
agent-service	33.34% <ø> (-1.02%)	⬇️	Carriedforward from cd60535
amber	53.26% <ø> (-0.51%)	⬇️	Carriedforward from cd60535
computing-unit-managing-service	1.65% <ø> (ø)		Carriedforward from cd60535
config-service	55.38% <ø> (-1.34%)	⬇️	Carriedforward from cd60535
file-service	39.34% <ø> (-17.73%)	⬇️	Carriedforward from cd60535
frontend	47.38% <5.55%> (+<0.01%)	⬆️
pyamber	90.70% <ø> (-0.02%)	⬇️	Carriedforward from cd60535
python	90.74% <ø> (ø)		Carriedforward from cd60535
workflow-compiling-service	58.69% <ø> (ø)		Carriedforward from cd60535

*This pull request uses carry forward flags. Click here to find out more.

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[kunwp1]

Seems like this PR is depends on #5613 so I'll review this PR after it's merged.