FIX: Show installation guide instead of exiting when no scanners detected

CRITICAL FIX: Standalone malware scanner was exiting with code 1 when no
scanners were installed, instead of showing helpful installation instructions.

Changes:
- Replaced hard exit with graceful exit code 0
- Display full installation guide for all 4 scanners (ImunifyAV, ClamAV, Maldet, RKHunter)
- Provide copy-paste installation commands for both RHEL and Debian systems
- Users can now see how to install scanners instead of seeing error exit

This ensures the malware scanner is user-friendly even on fresh systems.

Testing: Beta branch only (per user request - no production pushes during testing)

modules/security/malware-scanner.sh

@@ -100,7 +100,7 @@ detect_scanners() {
     return 0
 }
 
-# Show installation instructions for missing scanners
+# Show installation instructions for missing scanners (DEPRECATED - menu always shows now)
 show_scanner_installation_guide() {
     echo -e "${YELLOW}Available Malware Scanners:${NC}"
     echo ""
@@ -915,10 +915,51 @@ else
     fi
 fi
 
+# If no scanners found, show installation guide and exit gracefully
 if [ ${#AVAILABLE_SCANNERS[@]} -eq 0 ]; then
-    log_message "ERROR: No scanners found!"
+    log_message "WARNING: No scanners found on this system"
+    echo ""
     echo -e "${RED}No malware scanners detected!${NC}"
-    exit 1
+    echo ""
+    echo -e "${YELLOW}Available Malware Scanners:${NC}"
+    echo ""
+
+    echo -e "${CYAN}ImunifyAV${NC} - FREE real-time malware scanner"
+    echo "  Status: Not installed"
+    echo "  Installation (cPanel):"
+    echo "    yum install imunify-antivirus imunify-antivirus-cpanel"
+    echo "    /opt/alt/python35/share/imunify360/scripts/av-userside-plugin.sh"
+    echo "  Installation (manual):"
+    echo "    wget https://repo.imunify360.cloudlinux.com/defence360/imav-deploy.sh"
+    echo "    bash imav-deploy.sh"
+    echo "  Docs: https://docs.imunify360.com/imunifyav/"
+    echo ""
+
+    echo -e "${CYAN}ClamAV${NC} - Open source antivirus engine"
+    echo "  Status: Not installed"
+    echo "  Installation:"
+    echo "    yum install clamav clamav-update  # RHEL/CentOS"
+    echo "    apt-get install clamav clamav-daemon  # Debian/Ubuntu"
+    echo ""
+
+    echo -e "${CYAN}Maldet (LMD)${NC} - Linux Malware Detect"
+    echo "  Status: Not installed"
+    echo "  Installation:"
+    echo "    cd /tmp && wget http://www.rfxn.com/downloads/maldetect-current.tar.gz"
+    echo "    tar -xzf maldetect-current.tar.gz && cd maldetect-*"
+    echo "    ./install.sh"
+    echo ""
+
+    echo -e "${CYAN}Rootkit Hunter${NC} - Rootkit/backdoor/exploit scanner"
+    echo "  Status: Not installed"
+    echo "  Installation:"
+    echo "    yum install epel-release rkhunter  # RHEL/CentOS"
+    echo "    apt-get install rkhunter  # Debian/Ubuntu"
+    echo ""
+
+    echo -e "${YELLOW}Recommendation:${NC} Install at least ClamAV + RKHunter (both free)"
+    echo ""
+    exit 0
 fi
 
 log_message "Found ${#AVAILABLE_SCANNERS[@]} scanner(s): ${AVAILABLE_SCANNERS[*]}"