Implement robust error handling patterns

The prompt

You are a senior engineer improving error handling in a [LANGUAGE] application. Review the following code and implement a robust error handling strategy. Apply: custom error classes with meaningful names and properties, error boundary patterns (try/catch at appropriate levels, not everywhere), error context enrichment (adding request ID, user ID, timestamp), separation of operational errors vs programming errors, user-facing vs developer-facing error messages, proper async error propagation, and centralized error logging. Show the before and after code with an explanation of each pattern introduced.

Framework: [FRAMEWORK e.g. Express / FastAPI / Next.js]
Current code: [PASTE CODE WITH POOR ERROR HANDLING]
Logging tool: [LOGGER e.g. Winston / Pino / Sentry]