feat: add BlogPostLayout, ShareButtons, and blog data schema

[KaparthyReddy]

What does this PR do?

Implements the foundational blog architecture proposed in #17:

• src/data/blog.js — structured blog post schema following the existing mentors.js pattern, with fields for title, slug, date, read time, category, cover image, and author
• src/components/BlogPostLayout.jsx — reusable article layout built with Tailwind CSS, handling responsive typography, semantic <article> tags, pre-sized image slots (16/9 aspect ratio) to prevent CLS, and dynamic metadata rendering
• src/components/ShareButtons.jsx — social sharing component supporting Twitter/X, LinkedIn, WhatsApp, Copy Link with clipboard toast, and navigator.share native share API on supported mobile browsers
• src/components/Blog.jsx — blog section with card grid and click-through to full post layout

Type of change

• ✨ New feature
• 🎨 Style / UI improvement

Checklist

• I've tested my changes locally (npm run dev)
• My code follows the project style guide
• I've added/updated comments where needed
• No console errors introduced

Screenshots (if UI change)

Related issue

Closes #17

[vercel]

@KaparthyReddy is attempting to deploy a commit to the HerStack's projects Team on Vercel.

A member of the Team first needs to authorize it.

[KaparthyReddy]

Hi @escher-m, the PR is ready for review and has zero merge conflicts! It looks like the Vercel deployment check is currently on hold waiting for a team member to authorize the preview build.

Could you please trigger the authorization whenever you get a moment to review? Thank you!