🎨 Palette: Add active states to interactive elements

[keough99]

💡 What: Added :active states to the .btn and .social-card components in assets/style.css.
🎯 Why: To provide continuous, satisfying tactile feedback during user interactions by complementing the existing :hover transform states with a "press" state.
📸 Before/After: Before, buttons and cards only scaled up or moved up on hover but did not respond visually when clicked. After, they scale down or return to their original position when clicked.
♿ Accessibility: Improves visual feedback for mouse users, clarifying when an action has been successfully triggered.

---

PR created automatically by Jules for task 8207147743478892455 started by @keough99

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.