Use corev1.PullPolicy for EmbeddingServer ImagePullPolicy

[qorexdev]

Summary

ImagePullPolicy on EmbeddingServerSpec was typed as string, which meant no compile-time safety when comparing against corev1.PullAlways etc. Changed it to corev1.PullPolicy to match how upstream k8s types define this field. Updated GetImagePullPolicy() return type, removed the now-unnecessary cast in the controller, and switched tests to use typed constants.

Closes #4616

Type of change

• Refactoring (no behavior change)

Test plan

• Unit tests (task test)

Does this introduce a user-facing change?

No

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.92%. Comparing base (4529b8e) to head (bde2c08).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4649      +/-   ##
==========================================
+ Coverage   68.85%   68.92%   +0.06%     
==========================================
  Files         506      506              
  Lines       52449    52449              
==========================================
+ Hits        36115    36148      +33     
+ Misses      13542    13509      -33     
  Partials     2792     2792              

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[ChrisJBurns]

@qorexdev You have to run task operator-manifests, task crdref-gen and task docs to make sure the CRD and CRD docs are up to doc

[qorexdev]

Thanks for pointing that out! I don't have the task runner set up locally right now — will get it installed and regenerate the CRD docs soon.