improve: handle both pulse and pulse-backend service names gracefully

- ProxmoxVE community script uses pulse-backend.service
- Our install script now detects and preserves existing service name
- Removed pulse-backend.service from pre-v4 detection (it's used by v4 too)
- Install script stops the correct service during upgrades
- New installs use 'pulse', existing use whatever they have

This ensures compatibility with all deployment methods without breaking changes.

install.sh

@@ -19,6 +19,17 @@ SERVICE_NAME="pulse"
 GITHUB_REPO="rcourtman/Pulse"
 REQUIRED_GO_VERSION="1.21"
 
+# Detect existing service name (pulse or pulse-backend)
+detect_service_name() {
+    if systemctl list-unit-files --no-legend | grep -q "^pulse-backend.service"; then
+        echo "pulse-backend"
+    elif systemctl list-unit-files --no-legend | grep -q "^pulse.service"; then
+        echo "pulse"
+    else
+        echo "pulse"  # Default for new installations
+    fi
+}
+
 # Functions
 print_header() {
     echo -e "${BLUE}=================================================${NC}"
@@ -219,10 +230,13 @@ download_pulse() {
         exit 1
     fi
     
+    # Detect existing service name
+    EXISTING_SERVICE=$(detect_service_name)
+    
     # Stop service if running (for updates)
-    if systemctl is-active --quiet $SERVICE_NAME; then
-        print_info "Stopping existing Pulse service..."
-        systemctl stop $SERVICE_NAME
+    if systemctl is-active --quiet $EXISTING_SERVICE; then
+        print_info "Stopping existing Pulse service ($EXISTING_SERVICE)..."
+        systemctl stop $EXISTING_SERVICE
     fi
     
     # Extract to temporary directory first
@@ -277,6 +291,14 @@ setup_directories() {
 install_systemd_service() {
     print_info "Installing systemd service..."
     
+    # Use existing service name if found, otherwise use default
+    EXISTING_SERVICE=$(detect_service_name)
+    if [[ "$EXISTING_SERVICE" == "pulse-backend" ]] && [[ -f "/etc/systemd/system/pulse-backend.service" ]]; then
+        # Keep using pulse-backend for compatibility (ProxmoxVE)
+        SERVICE_NAME="pulse-backend"
+        print_info "Using existing service name: pulse-backend"
+    fi
+    
     cat > /etc/systemd/system/$SERVICE_NAME.service << EOF
 [Unit]
 Description=Pulse Monitoring Server

internal/updates/manager.go

@@ -689,11 +689,8 @@ func isPreV4Installation() bool {
 		return true
 	}
 	
-	// Check for old service names
-	cmd := exec.Command("systemctl", "list-unit-files", "--no-legend", "pulse-backend.service")
-	if output, err := cmd.Output(); err == nil && len(output) > 0 {
-		return true
-	}
+	// Note: pulse-backend.service is used by both v4 and pre-v4, so we can't use it as an indicator
+	// Only check for Node.js artifacts which are exclusive to pre-v4
 	
 	// Check for Node.js artifacts
 	nodeArtifacts := []string{