fix: add ^ and $ to patterns

[feloy]

when using ramalama (with --jinja flag for tools support) with this MCP server, this error happens:

got exception: {"code":500,"message":"JSON schema conversion failed:\nPattern must start with '^' and end with '$'\nPattern must start with '^' and end with '$'\nPattern must start with '^' and end with '$'\nPattern must start with '^' and end with '$'","type":"server_error"}
srv  log_server_r: request: POST /chat/completions 192.168.127.1 500

This PR adds ^ and $ to the patterns.

But I'm not sure it will continue to work, as the patterns do not support the expected strings, for example app=myapp,env=prod is not covered by pattern ^([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9]$