Add web GUI, docs, scripts, and 5G router config

- Web app (Flask): status, config, firewall, logs, users, restart
- Docs: AT commands, deploy, DNS, quickstart, web GUI
- Scripts: connect, deploy, diag, healthcheck, modem-status, speedtest, status, troubleshoot
- Init and iptables: 5g-router, 5g-webgui, rules.v4
- CHANGELOG, TODO, REVISION; config and README updates

web/run.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+# Run Alpine 5G Web GUI (Flask). Use from install dir, e.g. /usr/local/share/5g-webgui.
+cd "$(dirname "$0")"
+export FLASK_APP=app.py
+export PYTHONUNBUFFERED=1
+exec python3 -c "
+from app import app
+from auth_manager import init_default_users
+init_default_users()
+app.run(host='0.0.0.0', port=5000, threaded=True)
+"