Fix TypeScript errors that blocked builds

Fixed TypeScript typing in the changelog routes by casting request params to strings (apps/api/src/routes/v1/changelog) — resolved build errors that were preventing deployments.backend
Added an explicit router type annotation in the user routes (apps/api/src/routes/v1/user) to address a TypeScript inference issue and avoid type-related build failures.backend
Removed an unused express import from the user LLM config file (apps/api/src/routes/v1/user/llm-config) to clear a compiler warning.backend