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/templates/config.html

@@ -0,0 +1,12 @@
+{% extends "base.html" %}
+{% block title %}Config – Alpine 5G Router{% endblock %}
+{% block content %}
+<h2>Router config (/etc/5g-router.conf)</h2>
+<p style="color: var(--text-muted); margin: 0 0 1rem;">Edit and save. Keys and values only (one per line).</p>
+<textarea id="configEditor" class="config-editor" spellcheck="false"></textarea>
+<div class="actions">
+  <button type="button" class="btn btn-primary" id="saveConfig">Save config</button>
+  <button type="button" class="btn btn-secondary" id="loadConfig">Reload</button>
+</div>
+<div id="configMsg" class="msg"></div>
+{% endblock %}