feature : improved log setup failures with a fallback logger to os.Stderr

[redpinecube]

closes #41

Description

This PR improves robustness in logger setup by ensuring that createLogger never returns a nil logger even if:

• The log configuration file is missing or invalid
• The log directory cannot be created
• Log files cannot be opened

A fallback logger is returned that writes to stderr at DEBUG level ensuring the application can always safely log messages.