- Add MAX_CONFIG_SIZE constant (1 MiB) to limit single config file size
- Check file size via os.stat() before reading into memory
- Oversized files raise ConfigError with descriptive message instead of
being fully read (which could cause OOM with multi-GB files)
- Use single os.stat() call to get both mtime and size atomically
- Update README: document size limit in security mechanisms and notes
- Existing small configs (ini/json/yaml, typically <10KB) are unaffected
qing