Fix LabCoat landing page: use brand orange, correct source URL, match footer

- Replace all purple (#7c3aed) with brand accent (#d65a31)
- Fix GitLab source URL to https://gitlab.com/Commit451/LabCoat
- Match footer exactly with commit451.com (copyright + nav links)
- Use same background image, glow color, gradient-border styles
- Add mobile menu (hamburger) matching main site pattern
- Use article tags and backdrop-blur-sm on feature cards like main site

Author: VeldtJumper