feat: Initial release of the 'Days of Love' Streamlit app

[XYZChazan]

This commit introduces the full version of the relationship day counter application.

Key features include:

• A simple, two-column layout for input and results.
• Core function to calculate the total days elapsed since a user-defined start date.
• Highly visible, stylized success message (red background, centered white text).
• Image display with a download button for easy sharing.
• HTML/JavaScript component for copying the celebration text to the clipboard.
• Includes 'app.py' and 'requirements.txt'."