feat(index-check): add index check functionality before query

[Crushdada]

Summary

This PR adds a new indexCheck configuration option that enforces MongoDB queries to use indexes, preventing collection scans (COLLSCAN) operations.

Changes

• ✅ Added indexCheck helper functions in src/helpers/indexCheck.ts
• ✅ Updated 5 MongoDB operations to support index checking: deleteMany, aggregate, count, find, updateMany
• ✅ Added configuration support in .smithery/smithery.yaml
• ✅ Updated README.md with comprehensive documentation
• ✅ Added comprehensive test suite with 7 passing tests

Features

• Uses MongoDB's explain functionality to analyze query plans
• Configurable via environment variables, CLI args, or platform config
• Comprehensive error messages for debugging
• Only applies to query operations (not inserts)

Testing

• All existing tests pass
• New unit tests achieve 57.89% code coverage
• Integration tested with MCP server

Related Issues

Resolves #287

Documentation

• Updated README.md with indexCheck configuration details
• Added comprehensive examples and usage instructions
• Updated .smithery/smithery.yaml following project patterns