Require explicit authentication configuration in VirtualMCPServer

[yrobla]

Make IncomingAuth required in VirtualMCPServer CRD to enforce explicit
authentication decisions. Users must specify auth type even for anonymous.

Fixes #2843

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.58%. Comparing base (a5ff43f) to head (19ded00).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2865      +/-   ##
==========================================
- Coverage   56.66%   56.58%   -0.08%     
==========================================
  Files         322      322              
  Lines       31279    31439     +160     
==========================================
+ Hits        17723    17790      +67     
- Misses      12038    12120      +82     
- Partials     1518     1529      +11     

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[jhrozek]

two nits inline, also let's change the PR text to reflect what the PR does now, I think github uses the PR text as the commit message if you squash