feat: initial commit — backend API + student cabinet frontend

- Go backend: auth (JWT), points earn/spend, QR token generation,
  partners, admin grant/stats endpoints with chi router
- Next.js 14 frontend: login, student dashboard, transaction history,
  QR display, partners list
- PostgreSQL migrations (4 tables), Redis cache, Docker Compose
- CORS middleware, role-based route protection, Zustand auth store

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/users/service.go

@@ -0,0 +1,51 @@
+package users
+
+import "context"
+
+// Service handles business logic for the users domain.
+type Service struct {
+	repo *Repository
+}
+
+// NewService creates a new users Service.
+func NewService(repo *Repository) *Service {
+	return &Service{repo: repo}
+}
+
+// Profile represents a student's public profile and current balance.
+type Profile struct {
+	ID        string `json:"id"`
+	Email     string `json:"email"`
+	Name      string `json:"name"`
+	StudentID string `json:"student_id,omitempty"`
+	Balance   int    `json:"balance"`
+}
+
+// Transaction represents a single point-earning or point-spending event.
+type Transaction struct {
+	ID          string `json:"id"`
+	Amount      int    `json:"amount"`
+	Type        string `json:"type"`
+	Description string `json:"description,omitempty"`
+	PartnerID   string `json:"partner_id,omitempty"`
+	CreatedAt   string `json:"created_at"`
+}
+
+// GetProfile returns the profile and current balance for the given user.
+func (s *Service) GetProfile(ctx context.Context, userID string) (*Profile, error) {
+	return s.repo.GetByID(ctx, userID)
+}
+
+// GetTransactions returns a paginated list of transactions for the given user
+// (newest first) together with the total row count for pagination metadata.
+func (s *Service) GetTransactions(ctx context.Context, userID string, limit, offset int) ([]Transaction, int, error) {
+	total, err := s.repo.CountTransactions(ctx, userID)
+	if err != nil {
+		return nil, 0, err
+	}
+	txs, err := s.repo.ListTransactions(ctx, userID, limit, offset)
+	if err != nil {
+		return nil, 0, err
+	}
+	return txs, total, nil
+}