[Phase 3.2] Study Streak System & Calendar

[robinson]

Goal

Track and display daily study streaks with a calendar heatmap that motivates
consistent studying without punishing missed days.

Design Principles

• Streaks restart gracefully — no shame messaging on break.
• "Freeze" mechanic: student earns one streak freeze per 7-day streak.
• Calendar shows activity density (light/medium/dark green), not raw scores.

Scope

• Backend: streaks table in SQLite; GET /streaks/:userId endpoint returns
  current streak, longest streak, and 90-day activity map.
• Frontend: Calendar heatmap widget (12-week view); streak counter in
  Home Dashboard; "streak saved" animation when freeze is used.

Acceptance Criteria

• Streak increments once per calendar day on any learning activity.
• Calendar heatmap renders correctly for a 90-day window.
• Streak freeze activates automatically on first missed day after a 7-day run.
• Streak counter visible on Home Dashboard.

References

• docs/UX_REDESIGN_STRATEGY.md — Part 5: Gamification (Study Streak Tracking)

Phase

Phase 3 — Gamification & Progress · Week 2–3