docs(teams-api): fix README inaccuracies against actual source

[rodmhgl]

Updates workshop/teams-management/teams-api/README.md to align with the actual deployment manifest and API behavior.

Deployment instructions:

• Changed kubectl apply -f k8s/ → kubectl apply -f deployment.yaml (no k8s/ subdirectory exists)

API response examples:

• Removed non-existent message and version fields from /health endpoint examples — actual response is {"status":
  "healthy", "teams_count": 0}

Troubleshooting:

• Corrected port-forward commands from :80 → :4200 to match the service's actual target port
• Added missing 400 error example for duplicate team name ("Team name already exists")

[Copilot]

Pull request overview

This pull request fixes documentation inaccuracies in the Teams API README by aligning deployment instructions, API response examples, and troubleshooting commands with the actual implementation and deployment manifests.

Changes:

• Updated deployment instructions to reference the correct file path (deployment.yaml instead of k8s/)
• Corrected health endpoint response examples to match actual API output (removed non-existent message and version fields)
• Fixed port-forward commands to use the correct service port (4200 instead of 80)
• Added missing error handling example for duplicate team names

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