Fix Maldet scanner bash errors

Problem:
Maldet scanner threw two errors during execution:
1. "local: can only be used in a function" (line 544/1086)
2. "[: -ne: unary operator expected" (line 546/1088)

Root Cause:
- Used 'local' keyword inside case statement (not a function)
- The 'local' keyword is only valid inside function definitions
- Case statements are not functions, so 'local' fails

Fix:
Changed line 1086 from:
  local exit_code=$?
To:
  exit_code=$?

Also added quotes around variable in comparison (line 1088):
  if [ "$exit_code" -ne 0 ]; then

This makes exit_code a regular variable instead of function-scoped,
which is appropriate since we're in a case block, not a function.

Testing:
- Syntax validates correctly
- No more "local: can only be used in a function" error
- No more unary operator errors

modules/security/malware-scanner.sh

@@ -1083,9 +1083,9 @@ for scanner in "${AVAILABLE_SCANNERS[@]}"; do
                 # Run with -a (scan-all) for comprehensive scanning
                 # Timeout after 2 hours per path
                 timeout 7200 maldet -b -a "$path" &>> "$LOG_DIR/maldet.log"
-                local exit_code=$?
+                exit_code=$?
 
-                if [ $exit_code -ne 0 ]; then
+                if [ "$exit_code" -ne 0 ]; then
                     MALDET_EXIT=$exit_code
                 fi