IMPROVEMENT: Enhanced installation verification and error visibility

Improves package manager installation logging and error reporting in
install_clamav_only() and install_rkhunter_only() functions.

Changes:
1. Capture full installation output to temporary log files
2. Explicitly check package manager exit codes
3. Display full output on success (tail -5/-3)
4. Display extended output on failure (tail -10) with warning
5. Clean up temporary log files after use

Benefits:
- Users can see installation output and diagnose failures
- Non-zero exit codes from package managers are visible
- Installation logs preserved for debugging if needed
- More transparent error handling for yum/apt-get operations

Example:
Before: yum install -y clamav 2>&1 | tail -5  (exit code hidden)
After:  Check exit code, show appropriate output on success/failure

Status: ✓ Syntax validated, improved error visibility

modules/security/malware-scanner.sh

@@ -524,11 +524,25 @@ install_clamav_only() {
 
     if command -v yum &>/dev/null; then
         echo "Using yum package manager..."
-        yum install -y clamav clamav-daemon clamav-update 2>&1 | tail -5
+        local install_log="/tmp/clamav-install-$$.log"
+        if yum install -y clamav clamav-daemon clamav-update > "$install_log" 2>&1; then
+            tail -5 "$install_log"
+        else
+            echo -e "${YELLOW}Installation returned non-zero exit code${NC}"
+            tail -10 "$install_log"
+        fi
+        rm -f "$install_log"
     elif command -v apt-get &>/dev/null; then
         echo "Using apt package manager..."
         apt-get update > /dev/null 2>&1
-        apt-get install -y clamav clamav-daemon 2>&1 | tail -5
+        local install_log="/tmp/clamav-install-$$.log"
+        if apt-get install -y clamav clamav-daemon > "$install_log" 2>&1; then
+            tail -5 "$install_log"
+        else
+            echo -e "${YELLOW}Installation returned non-zero exit code${NC}"
+            tail -10 "$install_log"
+        fi
+        rm -f "$install_log"
     else
         echo -e "${RED}✗ No compatible package manager found${NC}"
         echo ""
@@ -576,11 +590,25 @@ install_rkhunter_only() {
     if command -v yum &>/dev/null; then
         echo "Using yum package manager..."
         yum install -y epel-release 2>&1 > /dev/null || true
-        yum install -y rkhunter 2>&1 | tail -3
+        local install_log="/tmp/rkhunter-install-$$.log"
+        if yum install -y rkhunter > "$install_log" 2>&1; then
+            tail -3 "$install_log"
+        else
+            echo -e "${YELLOW}Installation returned non-zero exit code${NC}"
+            tail -10 "$install_log"
+        fi
+        rm -f "$install_log"
     elif command -v apt-get &>/dev/null; then
         echo "Using apt package manager..."
         apt-get update > /dev/null 2>&1
-        apt-get install -y rkhunter 2>&1 | tail -3
+        local install_log="/tmp/rkhunter-install-$$.log"
+        if apt-get install -y rkhunter > "$install_log" 2>&1; then
+            tail -3 "$install_log"
+        else
+            echo -e "${YELLOW}Installation returned non-zero exit code${NC}"
+            tail -10 "$install_log"
+        fi
+        rm -f "$install_log"
     else
         echo -e "${RED}✗ No compatible package manager found${NC}"
         echo ""