feat: add loading skeleton for Repository Dashboard

[AliMahmoudDev]

Summary

Closes #3

Adds a loading.tsx file that displays a skeleton UI while the dashboard server component fetches data.

What it does

• Creates apps/web/src/app/dashboard/loading.tsx following the Next.js App Router convention
• The skeleton mirrors the exact layout of the dashboard page:
  • Metrics section: 4 cards with pulsing label and value placeholders matching the "Tracked Repositories", "Commits", "Open PRs", and "Closed PRs" cards
  • Repositories section: 6 cards with name, full name, visibility badge, and sync status placeholders
• Uses animate-pulse from Tailwind CSS for smooth pulsing animation
• Skeleton dimensions match the final rendered cards, preventing layout shift when data arrives

Design decisions

• Used Next.js loading.tsx convention instead of a separate component + isLoading check, since the dashboard page is a server component (async function) — React Suspense with loading.tsx is the idiomatic approach
• Gray-200 and gray-100 backgrounds to match the existing card border/shadow aesthetic
• 6 repo card skeletons to match a typical 3-column grid with 2 rows

[SHAURYASANYAL3]

Hey @AliMahmoudDev
It looks like you accidentally opened two Pull Requests for this feature. I just reviewed and merged your other
one (PR #35) because you included the awesome repository/[id]/loading.tsx file in that one as well!

I'm going to close this specific PR as a duplicate, but your code is already going to be merged into main via
PR
#35. Thank you again for the amazing first contribution! 🌟

Make sure to join our Discord to hang out with the team: https://discord.gg/D2jCpbYgQJ

[AliMahmoudDev]

Good PR for the Forge-Lens dashboard! The component looks well-structured. One thought: adding TypeScript interfaces for the props would make the component easier to use and catch type errors at compile time.