fix: remove unused import and variable flagged by go vet

Remove unused repository import from discovery_handler_test.go and
unused tests variable from discovery_test.go (replaced by testCases).

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

internal/api/handler/discovery_handler_test.go

@@ -12,7 +12,6 @@ import (
 
 	"github.com/shankar0123/certctl/internal/api/middleware"
 	"github.com/shankar0123/certctl/internal/domain"
-	"github.com/shankar0123/certctl/internal/repository"
 )
 
 // MockDiscoveryService is a mock implementation of DiscoveryService interface.

internal/domain/discovery_test.go

@@ -62,17 +62,6 @@ func TestDiscoveredCertificate_IsExpired(t *testing.T) {
 func TestDiscoveredCertificate_DaysUntilExpiry(t *testing.T) {
 	now := time.Now()
 
-	tests := []struct {
-		name     string
-		notAfter *time.Time
-		wantDays int
-	}{
-		{"nil NotAfter", nil, -1},
-		{"expires in 30 days", &time.Time{}, 0}, // placeholder, will be calculated below
-		{"expires in 1 day", &time.Time{}, 1},
-		{"expires in 0 days (expired)", &time.Time{}, 0},
-	}
-
 	// Test with actual future times
 	thirtyDaysFromNow := now.AddDate(0, 0, 30)
 	oneDayFromNow := now.AddDate(0, 0, 1)