added missing __main__ in mcp_server_sentry

[aliev]

Description

In the current implementation, the __main__.py file and the call to the main() function are missing. As a result, the example from the "Using pip" section in the README does not work:

(.venv) ➜  mcp_server_sentry python -m mcp_server_sentry
/Users/ali/examples/.venv/bin/python: No module named mcp_server_sentry.__main__; 'mcp_server_sentry' is a package and cannot be directly executed

The issue is resolved by adding the __main__.py file with the main() function calling, which is exactly what this PR does:

(.venv) ➜  mcp_server_sentry python -m mcp_server_sentry
Usage: python -m mcp_server_sentry [OPTIONS]
Try 'python -m mcp_server_sentry --help' for help.

Error: Missing option '--auth-token'.
(.venv) ➜  mcp_server_sentry 

Server Details

• Server: mcp_server_sentry
• Changes to: mcp_server_sentry

Motivation and Context

How Has This Been Tested?

Breaking Changes

Types of changes

• New MCP Server
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Protocol Documentation
• My server follows MCP security best practices
• I have updated the server's README accordingly
• I have tested this with an LLM client
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have documented all environment variables and configuration options

Additional context

[jspahrsummers]

Thank you!