docs: improve model management documentation

[ChenYi015]

Purpose of this PR

Improve the Model Management documentation to provide a better onboarding experience for users with clearer structure, comprehensive examples, and practical guidance.

Proposed changes:

• Added Overview section explaining Arena's unified model management system capabilities
• Improved "Who Should Use This Guide" section with specific use cases
• Reformatted Prerequisites section with numbered steps for better readability
• Added complete Model Lifecycle Workflow section with end-to-end examples covering training, querying, deployment, and monitoring
• Added Best Practices section covering naming conventions, tagging strategies, version control, and cleanup
• Added Troubleshooting section with solutions for common MLflow connectivity and authentication issues
• Added Integration Examples section linking to related documentation
• Added See Also section for quick navigation to related guides
• Fixed typos ("Manage" -> "Management", "model" -> "models")

Change Category

• Bugfix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that could affect existing functionality)
• Documentation update

Rationale

The original documentation was minimal and lacked need comprehensive examples showing the complete model lifecycle from training to serving, along with best practices and troubleshooting tips. This update helps practical guidance. Users users understand how to effectively use Arena's model management features in their ML workflows.

[google-oss-prow]

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