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/init.d/5g-webgui

@@ -0,0 +1,27 @@
+#!/sbin/openrc-run
+# Alpine 5G Router – Web GUI (Flask). Login: admin/support with different permissions.
+# Rev: 1  (see REVISION in repo root)
+
+description="5G Router Web GUI (port 5000)"
+command="/usr/local/share/5g-webgui/run.sh"
+command_background="yes"
+pidfile="/run/5g-webgui.pid"
+output_log="/var/log/5g-webgui.log"
+error_log="/var/log/5g-webgui.log"
+
+depend() {
+    need net
+    after bootmisc
+}
+
+start_pre() {
+    if [ ! -f /usr/local/share/5g-webgui/app.py ]; then
+        eend 1 "Web GUI not installed at /usr/local/share/5g-webgui"
+        return 1
+    fi
+    if ! command -v python3 >/dev/null 2>&1; then
+        eend 1 "python3 not found. Install: apk add python3 py3-flask"
+        return 1
+    fi
+    return 0
+}