feat: Allow communication between sessions of same user

[MoritzWeber0]

A requirement for the training mode is that a Jupyter session can talk to a Capella session.

This PR adds network policies so that Pods can reach the ports of other Pods from the same user.

[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 SonarCloud

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 83.96%. Comparing base (d514394) to head (4906bab).
Report is 313 commits behind head on main.

Files with missing lines	Patch %	Lines
backend/capellacollab/sessions/operators/k8s.py	55.55%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1708      +/-   ##
==========================================
- Coverage   83.97%   83.96%   -0.02%     
==========================================
  Files         184      185       +1     
  Lines        6085     6105      +20     
  Branches      673      674       +1     
==========================================
+ Hits         5110     5126      +16     
- Misses        827      831       +4     
  Partials      148      148              

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