feat: add release management tools (#181)

* feat: add release management tools

* docs: clarify release_date and target_date fields in release management tools

* feat: implement removal functionality for release item labels and work items

* refactor: remove release comment and link tools from the Plane MCP Server

* refactor: simplify release-related tools documentation in Plane MCP Server

* feat: add changelog tools and enhance HTML description handling in release management

* refactor: remove release changelog tests and related tools from integration tests