test : added unit tests for streak.ts

[tmdeveloper007]

Closes #2771.

Summary of What Has Been Done:
Added comprehensive unit tests for the streak calculation functions in src/lib/streak.ts: calculateStreakFromDates(), calculateCurrentStreak(), and calculateStreak().

Changes Made:

• Added test/streak.test.ts with 10 test cases across 3 describe blocks
• calculateStreakFromDates(): empty input, single day, consecutive streak, gap breaks, freeze dates bridging gaps, current streak zero when last active is older than yesterday
• calculateCurrentStreak(): Set and array input, deduplication of ISO timestamps, empty input returns 0
• calculateStreak(): Date[] adapter, delegates to calculateStreakFromDates

Impact it Made:
Improves test coverage for the streak calculation system that powers the user dashboard streak widgets. Ensures consecutive-day counting and freeze-date handling are accurate.

[github-actions]

GSSoC Label Checklist 🏷️

@Umbrella-io — 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

[github-actions]

🎉 Merged! Thanks for contributing to DevTrack.

If the project has been useful to you, a ⭐ star on the repo is the easiest way to support it — it helps DevTrack get discovered by more developers.

Keep an eye on open issues for your next contribution!