Harden the four monitoring scripts

set -euo pipefail across all four, but added deliberately rather than
pasted in -- each script needed the places where a non-zero exit is
normal handled first, or strict mode would have made them worse:

- sys_monitor / process_monitor: `ps | head -n 6` is a latent SIGPIPE.
  head closes the pipe after six lines, and on a host with enough
  processes ps fills the buffer and exits 141, which pipefail turns into
  a script abort -- on exactly the busy machine you wanted to inspect.
  Confirmed the mechanism (a large producer into head returns 141) and
  those pipelines now tolerate it.
- security_audit: find exits non-zero when it cannot read a directory,
  which is routine when walking the whole filesystem. Without handling,
  set -e aborted the audit part way while still looking complete. Also
  notes that a clean report as non-root means little, since find cannot
  descend where it may not read.
- network_info: iptables needs root, so the last section aborted the
  script for ordinary users. Now reports the failure, and falls back to
  nft where iptables is absent.

process_monitor also no longer kills on sight. `pkill -x` by name can
match several processes at once, and as root that is an easy way to take
down more than intended. It now prints what it matched and asks, with
FORCE=1 for unattended use and a refusal rather than a hang when there
is no tty.

All four run clean; the kill path was tested against a live process and
left it alive.

sys_monitor.sh

@@ -17,7 +17,15 @@
 # 
 # Usage: sys_monitor.sh    (no arguments)
 # Description: Prints system uptime, memory, disk usage, and top CPU/mem processes.
- 
+
+set -euo pipefail
+
+# `ps | head` is a SIGPIPE waiting to happen: head closes the pipe after
+# six lines, and on a host with enough processes ps fills the buffer and
+# dies with 141, which pipefail turns into a script exit. That is exactly
+# the busy machine you most want this to work on, so those two pipelines
+# tolerate it explicitly.
+
 echo "==== System Uptime and Load ===="
 uptime
 
@@ -30,7 +38,7 @@ df -h -x tmpfs -x devtmpfs
 
 echo -e "\n==== Top 5 Processes by CPU Usage ===="
 # Display header and top 5 CPU-consuming processes
-ps -eo pid,user,comm,%cpu --sort=-%cpu | head -n 6
+ps -eo pid,user,comm,%cpu --sort=-%cpu | head -n 6 || true
 
 echo -e "\n==== Top 5 Processes by Memory Usage ===="
-ps -eo pid,user,comm,%mem --sort=-%mem | head -n 6
+ps -eo pid,user,comm,%mem --sort=-%mem | head -n 6 || true