feat: add RedisVL MCP server and documentation

[vishal-bala]

Summary

• Add a RedisVL MCP server, CLI entrypoint, configuration models, error handling, filter parsing, and search-records / upsert-records tools
• Document how to run and configure MCP, including a new concepts page, a how-to guide, README updates, installation notes, and aligned spec examples
• Cover the pain point of reimplementing Redis retrieval logic in each MCP client by exposing an existing Redis index through a stable, configuration-owned tool surface
• Add unit and integration coverage for startup, config validation, search, upsert, filters, settings, and CLI behavior

Testing

• make docs-build
• Not run (not requested)

[jit-ci]

🛡️ Jit Security Scan Results

✅ No security findings were detected in this PR

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^{Security scan by Jit}