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/firewall.html

@@ -0,0 +1,32 @@
+{% extends "base.html" %}
+{% block title %}Firewall – Alpine 5G Router{% endblock %}
+{% block content %}
+<h2>Firewall rules (iptables)</h2>
+<p style="color: var(--text-muted); margin: 0 0 1rem;">Rules are stored in SQLite. Add rules below, then click Apply to write /etc/iptables/rules.v4 and run iptables-restore.</p>
+
+<div class="table-wrap">
+  <table>
+    <thead>
+      <tr><th>Table</th><th>Rule</th><th>Enabled</th><th>Actions</th></tr>
+    </thead>
+    <tbody id="firewallTable"></tbody>
+  </table>
+</div>
+
+<div class="panel-form" style="margin-top: 1rem;">
+  <h3 style="font-size: 0.9375rem; margin: 0 0 0.5rem;">Add rule</h3>
+  <div class="form-row">
+    <select id="firewallTableName">
+      <option value="filter">filter</option>
+      <option value="nat">nat</option>
+    </select>
+    <input type="text" id="firewallRuleLine" placeholder="-A FORWARD -i eth0.100 -o eth1 -j ACCEPT" style="flex: 1; min-width: 200px;">
+    <button type="button" class="btn btn-primary" id="firewallAddBtn">Add</button>
+  </div>
+</div>
+
+<div class="actions" style="margin-top: 1rem;">
+  <button type="button" class="btn btn-primary" id="firewallApplyBtn">Apply to system</button>
+</div>
+<div id="firewallMsg" class="msg"></div>
+{% endblock %}