Organize backend into product executable and shared Go modules

backend/product/verification/store/hash_test.go

@@ -0,0 +1,19 @@
+package verification
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTokenHash_Deterministic(t *testing.T) {
+	h1 := tokenHash("same-input")
+	h2 := tokenHash("same-input")
+	assert.Equal(t, h1, h2)
+}
+
+func TestTokenHash_DifferentInputs(t *testing.T) {
+	h1 := tokenHash("input-a")
+	h2 := tokenHash("input-b")
+	assert.NotEqual(t, h1, h2)
+}