Polish home page UI and setup config

[dinithrathnayaka23]

Summary

• Added project setup requirements files for runtime and development dependencies.
• Improved the home page navbar, hero section, content cards, and floating controls.
• Added Font Awesome icons and cleaner visual hierarchy across the non-footer UI.

Changes

• Added requirements.txt and requirements-dev.txt.
• Updated .gitignore to ignore venv/ and local Flask server logs.
• Reworked navbar layout, hover effects, and sticky spacing.
• Organized hero stats, status widgets, feature cards, capability cards, and the “3 steps to climate resilience” section.
• Replaced unclear symbols/abstract visuals with clearer Font Awesome-based icons.
• Improved back-to-top button styling and prevented overlap when the chatbot is open.

Testing

• Verified the Flask app loads locally at http://127.0.0.1:5000/.
• Checked responsive desktop and mobile layouts with local browser screenshots.
• Confirmed backend smoke check returned 200 OK.