READONLY mode support is needed in dotnet MCP server as implemented in Node version

[brano]

Could you please implement support for READONLY mode in dotnet version? So that when env configuration is configured with "READONLY": "true" MCP server will not allow to execute Update/Insert/Drop tools.

"env": {
    "CONNECTION_STRING": "Server=localdev;Database=eCommerce;Integrated Security=True;TrustServerCertificate=True;Encrypt=False",
    "READONLY": "true"
}

dotnet version: https://github.com/Azure-Samples/SQL-AI-samples/blob/5a4ba3f8d62aa5683a497f16e5ff4c26cc600ee0/MssqlMcp/dotnet/MssqlMcp/Program.cs#L37

Node version: https://github.com/Azure-Samples/SQL-AI-samples/blob/5a4ba3f8d62aa5683a497f16e5ff4c26cc600ee0/MssqlMcp/Node/src/index.ts#L85

[AV25242]

@stuartpa can you please take a look

[sitefinitysteve]

#64 Man not just READONLY, but the ReadData.cs tool had zero checks and balances unlike the TS one