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

REVISION

@@ -0,0 +1,18 @@
+# Alpine 5G Router – file revisions
+# Bump the rev in this file and in the file’s “Rev: N” line when you change a file.
+# On device, check installed rev: head -3 /usr/local/bin/modem-status-at.sh
+
+scripts/modem-status-at.sh    2
+scripts/status-5g.sh          1
+scripts/connect-5g.sh          2
+scripts/healthcheck-5g.sh      1
+scripts/speedtest-5g.sh        1
+scripts/rotate-5g-log.sh       1
+scripts/install.sh            1
+scripts/diag-at-port.sh        1
+scripts/diag-modem-up.sh       1
+etc/init.d/5g-router           5
+etc/init.d/5g-webgui           1
+configure_fm350_5g.sh          1
+web/app.py                    1
+web/static/app.js             2