fix: resolve golangci-lint errcheck warnings

- Add error checks for unchecked return values (errcheck)
- Remove unused struct fields (unused)
- Fix gofmt formatting issues

main_test.go

@@ -19,11 +19,11 @@ func TestVoiceRegistryRefresh(t *testing.T) {
 
 	// Create a voice directory
 	voiceDir := filepath.Join(dir, "test-voice")
-	os.MkdirAll(voiceDir, 0o755)
+	_ = os.MkdirAll(voiceDir, 0o755)
 	info := map[string]string{"name": "test-voice", "language": "en", "type": "coqui-tts", "created_at": "2024-01-01"}
 	infoData, _ := json.Marshal(info)
-	os.WriteFile(filepath.Join(voiceDir, "model_info.json"), infoData, 0o644)
-	os.WriteFile(filepath.Join(voiceDir, "model.pth"), []byte("fake"), 0o644)
+	_ = os.WriteFile(filepath.Join(voiceDir, "model_info.json"), infoData, 0o644)
+	_ = os.WriteFile(filepath.Join(voiceDir, "model.pth"), []byte("fake"), 0o644)
 
 	vr := newVoiceRegistry(dir)
 	count := vr.refresh()
@@ -59,10 +59,10 @@ func TestVoiceRegistryMissing(t *testing.T) {
 func TestVoiceRegistryNoModel(t *testing.T) {
 	dir := t.TempDir()
 	voiceDir := filepath.Join(dir, "bad-voice")
-	os.MkdirAll(voiceDir, 0o755)
+	_ = os.MkdirAll(voiceDir, 0o755)
 	info := map[string]string{"name": "bad-voice"}
 	infoData, _ := json.Marshal(info)
-	os.WriteFile(filepath.Join(voiceDir, "model_info.json"), infoData, 0o644)
+	_ = os.WriteFile(filepath.Join(voiceDir, "model_info.json"), infoData, 0o644)
 	// No model.pth
 
 	vr := newVoiceRegistry(dir)
@@ -82,12 +82,12 @@ func TestSynthesizeHTTP(t *testing.T) {
 		}
 
 		var payload map[string]any
-		json.NewDecoder(r.Body).Decode(&payload)
+		_ = json.NewDecoder(r.Body).Decode(&payload)
 		if payload["text"] != "hello" {
 			t.Errorf("unexpected text: %v", payload["text"])
 		}
 
-		w.Write([]byte{0x01, 0x02, 0x03, 0x04})
+		_, _ = w.Write([]byte{0x01, 0x02, 0x03, 0x04})
 	}))
 	defer ts.Close()
 
@@ -98,7 +98,7 @@ func TestSynthesizeHTTP(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 	if resp.StatusCode != 200 {
 		t.Errorf("status = %d, want 200", resp.StatusCode)
 	}