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

etc/iptables/rules.v4

@@ -0,0 +1,24 @@
+# Alpine 5G Router – iptables rules (IPv4)
+# Restored at boot by iptables-restore service. Generated/updated by connect-5g.sh or install.
+# Ensure 5G WAN interface is eth1 and LAN is eth0.100; adjust if different.
+
+*filter
+:INPUT ACCEPT [0:0]
+:FORWARD ACCEPT [0:0]
+:OUTPUT ACCEPT [0:0]
+# Allow web GUI (port 5000) from eth0 (management access)
+-A INPUT -i eth0 -p tcp --dport 5000 -j ACCEPT
+# Allow LAN -> WAN (5G)
+-A FORWARD -i eth0.100 -o eth1 -j ACCEPT
+# Allow established/related WAN -> LAN
+-A FORWARD -i eth1 -o eth0.100 -m state --state RELATED,ESTABLISHED -j ACCEPT
+COMMIT
+
+*nat
+:PREROUTING ACCEPT [0:0]
+:INPUT ACCEPT [0:0]
+:OUTPUT ACCEPT [0:0]
+:POSTROUTING ACCEPT [0:0]
+# NAT LAN traffic going out 5G
+-A POSTROUTING -o eth1 -j MASQUERADE
+COMMIT