Fix pipefail race condition: Add || true to grep display lines

CRITICAL FIXES:
- Line 63 (Exim): Added || true to frozen message display
- Line 102 (Postfix): Added || true to suspended message display
- Line 142 (Sendmail): Added || true to deferred message display

WHY THIS MATTERS:
With set -o pipefail enabled, if grep returns no matches (exit code 1),
the script exits instead of continuing. This happens when:
- Messages are counted and confirmed present (lines 60, 97, 137)
- But queue changes before display (race condition)
- grep finds no matches and returns 1
- Pipeline fails and script exits abnormally

SOLUTION:
Added || true to prevent script failure if messages disappear between
check and display. Script now continues gracefully with no messages shown
instead of terminating unexpectedly.

TESTING:
✅ Syntax validation: PASS
✅ All three grep display lines protected
✅ Script continues if queue changes mid-execution

modules/email/mail-queue-inspector.sh

@@ -60,7 +60,7 @@ if [ "$MTA" = "exim" ]; then
         frozen=$(eval "$SYS_MAIL_CMD_QUEUE_LIST" | grep -c "^\[frozen\]" 2>/dev/null || true)
         if [ "$frozen" -gt 0 ]; then
             print_warning "$frozen frozen messages found"
-            eval "$SYS_MAIL_CMD_QUEUE_LIST" | grep "^\[frozen\]" | head -10
+            eval "$SYS_MAIL_CMD_QUEUE_LIST" | grep "^\[frozen\]" | head -10 || true
         else
             print_success "No frozen messages"
         fi
@@ -99,7 +99,7 @@ elif [ "$MTA" = "postfix" ]; then
         if [ "$suspended" -gt 0 ]; then
             print_warning "$suspended suspended messages found (delivery deferred)"
             # Show message ID and first line of suspension reason
-            eval "$SYS_MAIL_CMD_QUEUE_LIST" | grep -B1 "delivery temporarily suspended" | head -20
+            eval "$SYS_MAIL_CMD_QUEUE_LIST" | grep -B1 "delivery temporarily suspended" | head -20 || true
         else
             print_success "No suspended messages"
         fi
@@ -139,7 +139,7 @@ elif [ "$MTA" = "sendmail" ]; then
         if [ "$deferred" -gt 0 ]; then
             print_warning "$deferred deferred messages found"
             # Show deferred message reasons (continuation lines starting with spaces and parenthesis)
-            eval "$SYS_MAIL_CMD_QUEUE_LIST" | grep "^[[:space:]]*(" | head -20
+            eval "$SYS_MAIL_CMD_QUEUE_LIST" | grep "^[[:space:]]*(" | head -20 || true
         else
             print_success "No deferred messages"
         fi