[FEAT] Add GitHub Discussions activity to dashboard metrics

[Muragesh-24]

Summary

Adds a new Community Discussions metrics card to the dashboard, backed by GitHub GraphQL, to show discussions started, accepted answers, and discussion comments. Also updates GitHub auth to request the read:discussion scope.

Closes #185

Type of Change

• New feature

Changes Made

• Added a new discussions metrics API route.
• Added a new dashboard card for discussion analytics with loading, error, and empty states.
• Updated GitHub auth scope to include read:discussion.
• Wired the new card into the PR/Issues metrics area of the dashboard.

How to Test

1. Sign out and sign back in so GitHub re-prompts for the updated read:discussion scope.
2. Open a repository with GitHub Discussions enabled and create a discussion.
3. Reply to the discussion and mark a response as the accepted answer.
4. Refresh the dashboard and confirm the new Community Discussions card shows non-zero counts.
5. If the repo/org does not have Discussions enabled, confirm the card falls back gracefully instead of failing.

Checklist

• Linked issue in summary
• npm run lint passes locally
• No TypeScript errors (npm run type-check)
• Self-reviewed the diff
• Added/updated tests if applicable

[vercel]

@Muragesh-24 is attempting to deploy a commit to the PRIYANSHU DOSHI's projects Team on Vercel.

A member of the Team first needs to authorize it.

[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — please apply the appropriate labels before merging:

Difficulty (pick one):

• level:beginner — 20 pts
• level:intermediate — 35 pts
• level:advanced — 55 pts
• level:critical — 80 pts

Quality (optional):

• quality:clean — ×1.2 multiplier
• quality:exceptional — ×1.5 multiplier

Validation (required to score):

• gssoc:approved — counts for points
• gssoc:invalid / gssoc:spam / gssoc:ai-slop — does not score

Type labels (type:*) are auto-detected from files and title. Review and adjust if needed.
Points formula: (difficulty × quality_multiplier) + type_bonus

[Priyanshu-byte-coder]

Missing EOF newline at the end of src/app/api/metrics/discussions/route.ts. Please add a newline after the last closing brace.

[Muragesh-24]

Missing EOF newline at the end of src/app/api/metrics/discussions/route.ts. Please add a newline after the last closing brace.

@Priyanshu-byte-coder now i added EOF endline in src/app/api/metrics/discussions/route.ts

[Priyanshu-byte-coder]

Two issues:

1. Missing EOF newline
2. Raw Tailwind red colors — replace with CSS vars:
   • border-red-500/20, bg-red-500/10, text-red-400, border-red-500/30, text-red-300, hover:bg-red-500/10 → use var(--destructive) and var(--border)