Resolved TypeScript errors that blocked Railway build

Bug Fixes

• Fixed a build failure on Railway by resolving TypeScript errors in the API.devops
• Casted route parameters (slug and id) to string in the changelog routes to prevent type errors during build.backend
• Added an explicit IRouter type to the user router to fix a TypeScript inference issue across builds.backend
• Removed an unused import from the LLM config route to clear a TypeScript warning.backend