fix: resolve all staticcheck issues (SA5011)

- Fixed nil pointer dereference warnings by using t.Fatal instead of t.Error
- In unified_test.go: Changed service nil check to use t.Fatal
- In clockdisplay_test.go: Changed request nil check to use t.Fatal

Using t.Fatal ensures test execution stops if pointer is nil,
eliminating possibility of subsequent nil pointer dereference.

Progress: Eliminated all 5 staticcheck issues
Total issues: 21 → 16 (24% improvement)

Remaining:
- gocyclo: 14 (complexity - requires refactoring)
- revive: 1 (DiscoveryService naming)
- unparam: 1 (client.post result parameter)

pkg/discovery/unified_test.go

@@ -13,7 +13,7 @@ func TestNewUnifiedDiscoveryService(t *testing.T) {
 	service := NewUnifiedDiscoveryService(cfg)
 
 	if service == nil {
-		t.Error("Expected service to be created, got nil")
+		t.Fatal("Expected service to be created, got nil")
 	}
 
 	if service.config != cfg {

pkg/models/clockdisplay_test.go

@@ -386,7 +386,7 @@ func TestNewClockDisplayRequest(t *testing.T) {
 	request := NewClockDisplayRequest()
 
 	if request == nil {
-		t.Error("Expected non-nil request")
+		t.Fatal("Expected non-nil request")
 	}
 
 	if request.Enabled != nil {