fix: resolve 8 new Codacy issues introduced by PR changes

shellcheck SC2034:
- first_time_install.sh: 'type' loop variable also unused in the wifi
  status loop (we previously fixed 'device' → '_' but left 'type').
  Changed to '_ _ state' since neither device nor type is referenced.

ESLint no-undef:
- app.js: typeof guards don't satisfy no-undef; added updateSystemStats
  to the /* global */ declaration alongside showNotification.

nosec annotation:
- web_interface/app.py: app.run(host='0.0.0.0') line changed when we
  fixed debug=True, giving it a new issue ID. Re-added # nosec B104.

pyflakes F401:
- scripts/dev/test_pillow_compat.py: ImageFilter was imported but never
  used in the smoke test. Removed from the import.

Codacy API suppressions (false positives on changed lines):
- disk_cache.py 0o660 chmod (2x): lines changed when # nosec B103 was
  added, producing new Semgrep issue IDs. Re-suppressed.
- pages_v3.py raw-html-concat: Semgrep does not recognise escape() as
  a sanitizer; the escape() call IS the correct fix.
- app.py flask 0.0.0.0: same line as B104 above; Semgrep rule also
  re-suppressed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

first_time_install.sh

@@ -1475,7 +1475,7 @@ echo "WiFi Connection Status:"
 if command -v nmcli >/dev/null 2>&1; then
     WIFI_STATUS=$(nmcli -t -f DEVICE,TYPE,STATE device status 2>/dev/null | grep -i wifi || echo "")
     if [ -n "$WIFI_STATUS" ]; then
-        echo "$WIFI_STATUS" | while IFS=':' read -r _ type state; do
+        echo "$WIFI_STATUS" | while IFS=':' read -r _ _ state; do
             if [ "$state" = "connected" ]; then
                 SSID=$(nmcli -t -f active,ssid device wifi 2>/dev/null | grep "^yes:" | cut -d: -f2 | head -1)
                 if [ -n "$SSID" ]; then