Add tool for update prompt

[tylerslater-io]

Adds a new tool to the MCP server for creating new Langfuse prompt versions and updating labels on existing ones, including promotion to production. This enhancement enables users to manage and deploy Langfuse prompts directly through the MCP server.

• Implements update-prompt tool with parameters for name, prompt content, version, type, config, labels, and tags.
• Allows creation of new prompt versions or updating labels on existing versions.
• Supports promoting prompt versions to production.
• Updates server version to 0.1.0.

[CLAassistant]

All committers have signed the CLA.

[tylerslater-io]

@marcklingen It looks like there haven't been any PRs approved since open sourcing this. Need assistance with a maintainer on it?