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/partners/repository.go

@@ -0,0 +1,86 @@
+package partners
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// ErrNotFound is returned when the requested partner does not exist.
+var ErrNotFound = errors.New("partner not found")
+
+// Repository handles database access for the partners domain.
+type Repository struct {
+	db *pgxpool.Pool
+}
+
+// NewRepository creates a new partners Repository.
+func NewRepository(db *pgxpool.Pool) *Repository {
+	return &Repository{db: db}
+}
+
+// ListActive fetches all partners where is_active = true, ordered alphabetically.
+func (r *Repository) ListActive(ctx context.Context) ([]Partner, error) {
+	rows, err := r.db.Query(ctx,
+		`SELECT id, name, address, max_spend_pct
+		 FROM partners
+		 WHERE is_active = true
+		 ORDER BY name`,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("repository.ListActive: %w", err)
+	}
+	defer rows.Close()
+
+	var ps []Partner
+	for rows.Next() {
+		var p Partner
+		if err := rows.Scan(&p.ID, &p.Name, &p.Address, &p.MaxSpendPct); err != nil {
+			return nil, fmt.Errorf("repository.ListActive: scan: %w", err)
+		}
+		ps = append(ps, p)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, fmt.Errorf("repository.ListActive: rows: %w", err)
+	}
+	return ps, nil
+}
+
+// GetByID fetches a single partner by its primary key.
+// Returns ErrNotFound if no partner exists with that ID.
+func (r *Repository) GetByID(ctx context.Context, id string) (*Partner, error) {
+	var p Partner
+	err := r.db.QueryRow(ctx,
+		`SELECT id, name, address, max_spend_pct
+		 FROM partners WHERE id = $1`,
+		id,
+	).Scan(&p.ID, &p.Name, &p.Address, &p.MaxSpendPct)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, ErrNotFound
+		}
+		return nil, fmt.Errorf("repository.GetByID: %w", err)
+	}
+	return &p, nil
+}
+
+// GetByUserID fetches the partner record associated with the given cashier user account.
+// Returns ErrNotFound if no partner is linked to that user.
+func (r *Repository) GetByUserID(ctx context.Context, userID string) (*Partner, error) {
+	var p Partner
+	err := r.db.QueryRow(ctx,
+		`SELECT id, name, address, max_spend_pct
+		 FROM partners WHERE user_id = $1`,
+		userID,
+	).Scan(&p.ID, &p.Name, &p.Address, &p.MaxSpendPct)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, ErrNotFound
+		}
+		return nil, fmt.Errorf("repository.GetByUserID: %w", err)
+	}
+	return &p, nil
+}