feat(dashboard): group analytics sections and rename headings

[singhanurag0317-bit]

Summary

Closes #1397

Problem

The dashboard had repetitive and overlapping section names:

• PR Breakdown and PR Review Time Trend appeared as two separate, unrelated cards with no indication they're both PR-related analytics.
• Top Repositories didn't communicate it was an analytics view.
• Commits by Time of Day was a verbose, implementation-specific name rather than a user-facing concept.
• Issue Metrics and PR Metrics used a generic "Metrics" suffix that didn't align with the analytics grouping strategy.

These naming issues made the dashboard feel cluttered and hard to scan.

Solution

Renamed all affected widget headings and the DASHBOARD_WIDGET_LABELS registry to group related metrics under clear analytic umbrella terms, exactly matching the acceptance criteria in #1397:

Before	After
Top Repositories	Repo Analytics
PR Metrics	PR Analytics
PR Breakdown	PR Analytics — Breakdown
PR Review Time Trend	PR Analytics — Review Trend
Commits by Time of Day	Activity Overview
Issue Metrics	Issue Analytics

The "PR Analytics" prefix on Breakdown and Review Trend cards makes the grouping relationship immediately obvious without requiring users to rearrange widgets.

Changes

• src/lib/dashboard-layout.ts: Updated DASHBOARD_WIDGET_LABELS for 6 widget IDs so the customizable dashboard panel shows updated names in its sidebar/settings
• src/components/PRMetrics.tsx: SectionHeader title "PR Metrics" → "PR Analytics"
• src/components/PRBreakdownChart.tsx: <h2> text "PR Breakdown" → "PR Analytics — Breakdown"
• src/components/PRReviewTrendChart.tsx: <h2> text "PR Review Time Trend" → "PR Analytics — Review Trend"
• src/components/TopRepos.tsx: SectionHeader title → "Repo Analytics"
• src/components/CommitTimeChart.tsx: <h2> text → "Activity Overview"
• src/components/IssueMetrics.tsx: any heading/label "Issue Metrics" → "Issue Analytics"

Testing

1. Open the dashboard — verify all renamed cards show the new headings.
2. Open Dashboard Settings / customise panel — verify the widget list shows updated names (pulled from DASHBOARD_WIDGET_LABELS).
3. Check that no duplicate or orphaned label references remain (search "PR Breakdown" / "PR Review Time Trend" / "Top Repositories" / "Commit Time" / "Issue Metrics" in the UI — none should appear).
4. Existing widget functionality (data fetching, charting, drag-and-drop order) is unaffected — only string labels were changed.

[vercel]

@singhanurag0317-bit is attempting to deploy a commit to the PRIYANSHU DOSHI's projects Team on Vercel.

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[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]

This PR now has merge conflicts after recent changes to dashboard-layout.ts and TopRepos.tsx were merged. Please rebase on main:

git fetch origin
git rebase origin/main