feat: Make Python Virtual Environment Persistent: Add Environments to Left Panel

[SarahAsad23]

What changes were proposed in this PR?

This PR introduces persistent Python Virtual Environments (PVEs) by moving them out of the Computing Unit (CU) lifecycle and storing them in the database.

Previously, PVEs were managed through Computing Units and existed only within the CU they were created in. As a result, PVEs were lost when the corresponding CU was terminated. This PR adds a new python_virtual_environments table to persist PVE configurations and introduces a dedicated dashboard interface for managing them.

Users can now create, view, update, and delete their own Python virtual environments through a new "Environments" page in the dashboard sidebar. PVE definitions are stored as user-owned resources in the database and can be managed independently of Computing Units.

Any related issues, documentation, discussions?

Related discussions and issues: #5360, #5361.

How was this PR tested?

Tested manually and tests added to PveResourceSpec.

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

Co-authored using: Claude Code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 47.82609% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 52.15%. Comparing base (564ccdb) to head (de5d222).

Files with missing lines	Patch %	Lines
...esource/pythonvirtualenvironment/PveResource.scala	0.00%	30 Missing ⚠️
...virtual-environment/virtual-environment.service.ts	0.00%	4 Missing ⚠️
...exera/service/resource/AccessControlResource.scala	0.00%	1 Missing ⚠️
...resource/pythonvirtualenvironment/PveManager.scala	96.42%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5577      +/-   ##
============================================
- Coverage     52.17%   52.15%   -0.03%     
+ Complexity     2482     2478       -4     
============================================
  Files          1068     1068              
  Lines         41311    41380      +69     
  Branches       4439     4448       +9     
============================================
+ Hits          21556    21583      +27     
- Misses        18490    18530      +40     
- Partials       1265     1267       +2     

Flag	Coverage Δ		*Carryforward flag
access-control-service	64.28% <0.00%> (-0.33%)	⬇️
agent-service	33.76% <ø> (ø)		Carriedforward from 5619875
amber	53.22% <46.55%> (-0.07%)	⬇️
computing-unit-managing-service	1.65% <ø> (ø)
config-service	56.06% <ø> (ø)
file-service	38.32% <ø> (ø)
frontend	46.43% <60.00%> (+<0.01%)	⬆️
pyamber	90.72% <ø> (ø)		Carriedforward from 5619875
python	90.75% <ø> (ø)		Carriedforward from 5619875
workflow-compiling-service	58.69% <ø> (ø)

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

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