feat: create Learning Track Card Component

[D240021]

Issue

Closes #194

Summary

Implemented a reusable Learning Track Card component for displaying track metadata and a primary call to action, aligned with the provided design (image, category pill, typography, metadata row, and purple “Start Learning” control).

Changes

• Added components/LearningTrackCard.tsx, a client component that composes next/image (16:9 via aspect-video), category badges for Beginner / Intermediate / Advanced, title, single-line description, lesson count and duration on one row, and a full-width Start Learning button styled with #9d17ff (hover and focus states).
• Card shell uses white background, rounded-xl, shadow, and overflow-hidden so the image matches the card corners; layout uses responsive padding and sizes on the image for different viewport widths.
• API: props for image (imageSrc, imageAlt), category, title, description, lessonCount, durationLabel, optional href (renders as Link) or onStartLearning (renders as <button>), and optional className on the root.

Notes

No integration into a specific page was part of this work; the component is ready to be imported wherever learning tracks are listed.

I remain open to any corrections or feedback you may have.