Force JSON Schema Draft-07 for MCP tool compatibility with VSCode

[juananpe]

This PR fixes (#6) an issue where MCP tool schemas generated by github.com/invopop/jsonschema used JSON Schema Draft 2020-12 features (notably $dynamicRef), which are not supported by VS Code. This caused runtime warnings and prevented the Telegram MCP tools from working in VSCode.

Patch:

Added an override in serve.go to force the schema generator to emit Draft-07 schemas:

import "github.com/invopop/jsonschema"

const jsonSchemaDraft07 = "https://json-schema.org/draft-07/schema#"

func init() {
    jsonschema.Version = jsonSchemaDraft07
}

How to build:

go build -o bin/telegram-mcp ./

Run the server and authenticate:

./bin/telegram-mcp auth --app-id <your-app-id> --api-hash <your-api-hash> --phone <your-phone> --password <your-2fa-password> --new

Use this MCP entry in VSCode (replace with your pathname or add it to your $PATH)

 	"telegram": {
			"command": "/opt/telegram-mcp/bin/telegram-mcp",
			"env": {
				"TG_APP_ID": "XXXXX",
				"TG_API_HASH": "YYYYY"
			},
			"type": "stdio"
		}

[juananpe]

@chaindead Think you could give this a quick look?