Write a configuration management module

The prompt

You are a software engineer building application configuration management. Write a configuration module for a [LANGUAGE] application that: loads config from multiple sources in priority order (environment variables > config file > defaults), validates all config values at startup using a schema (throw with a clear error listing ALL invalid/missing values — not just the first), provides type-safe access to config values (no string indexing), supports different config profiles (development, test, production), reloads certain config values at runtime without restart (feature flags, log levels), never logs secret values, and includes a generateEnvTemplate() function that outputs a .env.example with all keys and descriptions.

Config values needed: [LIST CONFIG KEYS, TYPES, AND DESCRIPTIONS]
Language: [LANGUAGE]
Config file format: [YAML / TOML / JSON / .ENV]