Refactor scripts and introduce Streamlit App

[Moodakk]

I have refactored the original concatenated Python files into individual modules inside /app/dental_assistant/ (e.g., bot.py, database.py, models.py, find_files.py, etc.).
I also created a new /app/dental_assistant/app.py Streamlit application with a UI in Ukrainian to act as the main front-end, fulfilling the user's intent to refactor and run the application. Hardcoded absolute paths (like C:\Users\...) were updated to use relative paths. The Streamlit app was verified to successfully boot on port 8501.

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PR created automatically by Jules for task 8674676204078443088 started by @Moodakk

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