fix: position footer at bottom of the page layout

[victor-arango]

📄 Description

Fixed the footer positioning to ensure it always stays at the bottom of the page, even when content is short.
Applied min-h-[calc(100vh-311px)], subtracting the combined height of the navbar and footer for accurate layout behavior.
You can see an example of the fix on the About page.

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📝 Change summary

• Applied min-h-[calc(100vh-311px)] to maintain footer at the bottom of the viewport
• Adjusted layout structure to properly calculate available content height
• Verified consistent footer behavior across desktop and mobile views
• Example available on /about

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📝 Types of changes

• [ ] 🐛 Bug fix
• [ ] 🚨 Breaking change
• [x] 🧹 Chore (layout adjustment / visual fix)
• [ ] ✨ New feature
• [ ] ⏫ Version upgrade
• [ ] 📝 Documentation

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🧪 How to test

1. Visit the About page (/about)
2. Scroll through pages with short and long content
3. Verify that the footer remains at the bottom of the viewport
4. Check both desktop and mobile views

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📸 Screenshots

Before

After

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