Add company branding and social media links to the website footer

Implements company branding with logo and updates social media links in base.html and main.css; adds company-icon.png.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: be495e61-6bf5-4f3f-959e-f1c221454012
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/149d8ed8-39e0-4c40-9c1a-3fa69d160086/3f3c8b25-82d2-4ea6-b399-e8bc6f55423b.jpg
