fix(template): cherry-pick python cea auth fix to dev

[Copilot]

Cherry-pick of #15379 to dev. The Python basic-custom-engine-agent playground template was missing the ANONYMOUS_ALLOWED setting, causing auth misconfiguration at deploy time.

Changes

• templates/vsc/python/basic-custom-engine-agent/m365agents.playground.yml.tpl: Add CONNECTIONS__SERVICE_CONNECTION__SETTINGS__ANONYMOUS_ALLOWED: "True" alongside the other SERVICE_CONNECTION__SETTINGS__* env vars in the file/createOrUpdateEnvironmentFile deploy step.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Cherry-pick] PR #15379 needs to be synchronized to other branches</issue_title>
<issue_description>

Cherry-pick Reminder

@tecton Hello!

This is an automatically created reminder. Your PR #15379 (fix(template): python cea auth) is being merged into the release/6.5 branch.

Please ensure to cherry-pick these changes to the following branches:

• cherry-pick fix(template): python cea auth #15379 to dev
• cherry-pick fix(template): python cea auth #15379 to release/vs1714p7

Steps to Follow:

1. Wait for the current PR to be merged.
2. Execute the following commands locally:

   git fetch origin
   git checkout <target_branch>
   git cherry-pick <commit_hash>
   git push origin <target_branch>

3. Or create a new PR to merge these changes into the above branches.

After completion, please check the items above ✓

Note: This is an automatically created issue. You can close this issue after completing all the operations.
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Cherry-pick] PR #15379 needs to be synchronized to other branches #15397

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.29%. Comparing base (f58aefa) to head (f151c94).
⚠️ Report is 5 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff            @@
##              dev   #15408    +/-   ##
========================================
  Coverage   89.29%   89.29%            
========================================
  Files         620      620            
  Lines       38084    38084            
  Branches     7561     7732   +171     
========================================
  Hits        34009    34009            
  Misses       1973     1973            
  Partials     2102     2102            

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