Update README to use port 8000 instead of 5000 for better macOS compatibility

[andyli11]

Summary

This PR updates the README.md to recommend using port 8000 instead of Flask’s default port 5000 when running the app locally. This avoids conflicts with the AirPlay Receiver on macOS Monterey and newer (2022+), which occupies port 5000.

Changes

• Switched flask run command to flask run --port=8000
• Updated local URLs to reflect port 8000

Underlying Issue

Using port 5000 on newer versions of macOS can cause Flask apps to silently fail with a 403 error. Switching to port 8000 ensures a smoother developer experience across platforms without needing manual system configuration.

Testing

• Verified that the app runs and is accessible at http://localhost:8000 and http://127.0.0.1:8000
• Confirmed that no conflicts occur on macOS