refactor(github): extract insights generation into standalone buildIn…

[BinduShree0514]

Description

Fixes #298

Extracted insight generation logic into a standalone buildInsights() helper.

Added independent tests for:

• streak > 3 path
• streak ≤ 3 path
• missing language fallback

getFullDashboardData() now delegates to buildInsights().

Pillar

• 🛠️ Other (Bug fix, refactoring, docs)

Visual Preview

N/A — backend refactor only.

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally.
• I have run npm test locally.
• My commits follow Conventional Commits format.

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[github-actions]

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[github-actions]

⚠️ Hey @BinduShree0514, this PR has merge conflicts with the main branch.

Please pull the latest changes and resolve the conflicts so we can review it!

git fetch origin
git rebase origin/main
# resolve any conflicts, then:
git push --force-with-lease

Once resolved, the needs-rebase label will be removed automatically on the next check. 🙌