style: fix additional staticcheck warnings

- Lowercase error messages (ST1005)
- Use context.Background() instead of nil (SA1012)
- Fix rand.Intn(1) which always returns 0 (SA4030)
- Remove unnecessary nil check before len() (S1009)

internal/api/system_settings.go

@@ -171,16 +171,16 @@ func validateSystemSettings(settings *config.SystemSettings, rawRequest map[stri
 	if val, ok := rawRequest["backupPollingInterval"]; ok {
 		if interval, ok := val.(float64); ok {
 			if interval < 0 {
-				return fmt.Errorf("Backup polling interval cannot be negative")
+				return fmt.Errorf("backup polling interval cannot be negative")
 			}
 			if interval > 0 && interval < 10 {
-				return fmt.Errorf("Backup polling interval must be at least 10 seconds")
+				return fmt.Errorf("backup polling interval must be at least 10 seconds")
 			}
 			if interval > 604800 {
-				return fmt.Errorf("Backup polling interval cannot exceed 604800 seconds (7 days)")
+				return fmt.Errorf("backup polling interval cannot exceed 604800 seconds (7 days)")
 			}
 		} else {
-			return fmt.Errorf("Backup polling interval must be a number")
+			return fmt.Errorf("backup polling interval must be a number")
 		}
 	}
 

internal/logging/logging_test.go

@@ -271,7 +271,7 @@ func TestWithLoggerNilContext(t *testing.T) {
 
 	Init(Config{})
 
-	ctx := WithLogger(nil, New("svc", WithWriter(io.Discard)))
+	ctx := WithLogger(context.Background(), New("svc", WithWriter(io.Discard)))
 	if ctx == nil {
 		t.Fatal("expected non-nil context")
 	}

internal/mock/generator.go

@@ -2970,7 +2970,7 @@ func generatePMGInstances() []models.PMGInstance {
 		edgeQueue := &models.PMGQueueStatus{
 			Active:    rand.Intn(2),
 			Deferred:  rand.Intn(5),
-			Hold:      rand.Intn(1),
+			Hold:      rand.Intn(2), // rand.Intn(1) always returns 0
 			Incoming:  rand.Intn(3),
 			Total:     0,
 			OldestAge: int64(rand.Intn(600)),

internal/models/converters_test.go

@@ -78,7 +78,7 @@ func TestCopyStringFloatMap(t *testing.T) {
 			}
 
 			// Verify it's a copy, not the same reference
-			if tc.input != nil && len(tc.input) > 0 {
+			if len(tc.input) > 0 {
 				for k := range result {
 					result[k] = 999.0
 					break

internal/notifications/notifications.go

@@ -2305,7 +2305,7 @@ func formatWebhookDuration(d time.Duration) string {
 // extractTelegramChatID extracts and validates the chat_id from a Telegram webhook URL
 func extractTelegramChatID(webhookURL string) (string, error) {
 	if !strings.Contains(webhookURL, "chat_id=") {
-		return "", fmt.Errorf("Telegram webhook URL missing chat_id parameter")
+		return "", fmt.Errorf("telegram webhook URL missing chat_id parameter")
 	}
 
 	u, err := url.Parse(webhookURL)