feat(backend): add domain store, learning services, and seed data

Persist LMS entities and implement hearts/watch rules plus curriculum bootstrap.

backend/internal/service/hearts.go

@@ -0,0 +1,94 @@
+package service
+
+import (
+	"context"
+	"time"
+
+	"pargar/backend/internal/config"
+	"pargar/backend/internal/models"
+	"pargar/backend/internal/store"
+)
+
+// HeartsService manages the fixed 3-heart pool and lockout.
+// Hearts do not regenerate over time — only a mentor/admin unlock restores them.
+type HeartsService struct {
+	store *store.Store
+}
+
+func NewHeartsService(st *store.Store, _ *config.Config) *HeartsService {
+	return &HeartsService{store: st}
+}
+
+// RefreshHearts is a no-op kept for call-site compatibility.
+// The game has no timed heart refill; the stored count is authoritative.
+func (h *HeartsService) RefreshHearts(_ context.Context, u *models.User) (*models.User, error) {
+	return u, nil
+}
+
+// ConsumeHearts decrements hearts for wrong answers; locks the account at 0.
+// Admin and mentor accounts have infinite hearts and are never locked by this path.
+// Returns the updated user and how many hearts were lost.
+func (h *HeartsService) ConsumeHearts(ctx context.Context, u *models.User, loss int) (*models.User, int, error) {
+	if u.Role.IsStaff() {
+		return u, 0, nil
+	}
+	if loss < 0 {
+		loss = 0
+	}
+	prev := u.Hearts
+	cur := prev - loss
+	if cur < 0 {
+		cur = 0
+	}
+	actualLost := prev - cur
+	if err := h.store.SetHearts(ctx, u.ID, cur); err != nil {
+		return nil, 0, err
+	}
+	u.Hearts = cur
+	if cur == 0 && !u.IsLocked {
+		locked, err := h.store.LockUser(ctx, u.ID)
+		if err != nil {
+			return nil, 0, err
+		}
+		return locked, actualLost, nil
+	}
+	return u, actualLost, nil
+}
+
+// Streak logic keyed on activity date.
+func UpdateStreak(ctx context.Context, st *store.Store, u *models.User) (*models.User, error) {
+	today := time.Now()
+	current, err := st.GetUserByID(ctx, u.ID)
+	if err != nil {
+		return nil, err
+	}
+	streak := current.StreakCurrent
+	longest := current.StreakLongest
+	if current.LastActivityDate != nil {
+		last := time.Date(current.LastActivityDate.Year(), current.LastActivityDate.Month(), current.LastActivityDate.Day(), 0, 0, 0, 0, time.UTC)
+		todayDate := time.Date(today.Year(), today.Month(), today.Day(), 0, 0, 0, 0, time.UTC)
+		diff := int(todayDate.Sub(last).Hours() / 24)
+		switch {
+		case diff == 0:
+			// already active today
+			return current, nil
+		case diff == 1:
+			streak++
+		default:
+			streak = 1
+		}
+	} else {
+		streak = 1
+	}
+	if streak > longest {
+		longest = streak
+	}
+	lastDate := today
+	if err := st.UpdateStreakOnly(ctx, current.ID, streak, longest, &lastDate); err != nil {
+		return nil, err
+	}
+	current.StreakCurrent = streak
+	current.StreakLongest = longest
+	current.LastActivityDate = &lastDate
+	return current, nil
+}