Door Camera Monitoring Python Upgrade

I have an existing Python-based front-door camera application written three years ago. The core still runs, yet the front-panel video preview now starts only intermittently, and I need several improvements before reinstalling it at the entrance of my home.

First, any time the system hears a door knock or recognises my key or fingerprint, I want it to play an audible alert through the small speaker mounted beneath the monitor and instantly overlay the word “Danger” in large red text on the live feed. Night-time reliability is equally important, so motion detection must react to very slight movement even in low-light conditions. In short, the software must stay awake, watchful and error-free twenty-four hours a day.

You will work directly with the original source files (I will upload them as an attachment) and deliver a cleaned-up, fully commented Python project that:

• starts the video panel every time the program launches,
• detects tiny motion changes day or night (OpenCV or similar),
• triggers the sound-and-message routine on knock, key turn or fingerprint events,
• logs any faults so I can trace future issues.

Please keep the existing folder structure unless there is a strong reason to refactor, and note any new dependencies you introduce in a requirements.txt. Once complete, send back the updated code and concise setup instructions so I can redeploy it on the Raspberry Pi at my front door without downtime.