feat(config): add logging configuration to .env.example

- Add LOG_LEVEL environment variable with possible values and usage guidance
- Improve redis host documentation for docker-compose compatibility

.env.example

@@ -11,6 +11,7 @@
 HOST=0.0.0.0
 
 # Redis connection (external or internal).
+# Host name 'redis' works with docker-compose.yml setup
 REDIS_HOST=redis
 REDIS_PORT=6379
 REDIS_DB=0
@@ -57,3 +58,8 @@ GOOGLE_CLIENT_SECRET=
 # GitHub SSO (get from GitHub Developer Settings)
 GITHUB_CLIENT_ID=
 GITHUB_CLIENT_SECRET=
+
+# Log level for application logging.
+# Possible values: debug, info, warning, error, critical
+# Set to 'info' or 'warning' for general use. Use 'debug' for troubleshooting.
+LOG_LEVEL=info