Add block explorer MCP documentation and update navigation (#690)

## Summary by Sourcery

Add a new Block Explorer MCP documentation page and update the
navigation metadata to include it.

Enhancements:
- Update content/docs/blockchain-and-ai/meta.json to register the new
Block Explorer MCP page in the site navigation.

Documentation:
- Introduce a comprehensive Block Explorer MCP guide covering AI-powered
blockchain queries, use cases, architecture, and troubleshooting.
- Include a Quick Start section with setup steps for the MCP server,
network configuration, AI platform integration, and testing.
- Add detailed advanced use cases for contract monitoring, compliance
reporting, DeFi analysis, and network performance.
- Provide an architecture overview with a diagram and explanations of
key components and security considerations.
- Add a Troubleshooting section addressing common setup issues,
connection failures, performance bottlenecks, and data indexing delays.

Co-authored-by: saeeddawod <saeed.dawod@gmail.com>

Author: SaeeDawod