chore(infra): integrate nestjs-pino for structured JSON logging

[devxsameer]

Closes #13

What was done

• Replaced the default NestJS logger with nestjs-pino
• Enabled structured JSON logging across the application
• Added automatic HTTP request logging (method, URL, status code, response time)
• Configured severity-based log levels:
  • info → 2xx responses
  • warn → 4xx responses
  • error → 5xx responses
• Added redaction for sensitive headers (authorization, cookie)
• Integrated structured exception logging via global HttpExceptionFilter
• Enabled pretty logs in development and JSON logs in production

Example Log Output

{
  "level": 30,
  "req": { "method": "GET", "url": "/api/v1/health" },
  "res": { "statusCode": 200 },
  "responseTime": 7,
  "msg": "request completed"
}

[Oluwaseyi89]

@devxsameer please, endeavour to star our repository if you haven't done so before.