chore(docker): change application port from 8000 to 8080

Update Dockerfile to expose and bind Gunicorn to port 8080 instead of 8000. This aligns the container port configuration with the expected deployment environment requirements.

Changes:
- Update EXPOSE directive to port 8080
- Update Gunicorn bind address to 0.0.0.0:8080

dockerfile

@@ -24,7 +24,7 @@ COPY . .
 RUN python manage.py collectstatic --noinput
 
 # Expose port
-EXPOSE 8000
+EXPOSE 8080
 
 # Run migrations and start Gunicorn
-CMD sh -c "python manage.py migrate && gunicorn booking_system.wsgi:application --bind 0.0.0.0:8000 --workers 3"
+CMD sh -c "python manage.py migrate && gunicorn booking_system.wsgi:application --bind 0.0.0.0:8080 --workers 3"