Add VLAN overview table to VLAN configuration page

Below the configuration form, a new table lists all configured VLANs
with their port memberships: Member, Tagged, Untagged, and PVID
columns. Port ranges are formatted compactly (e.g. "1-2,5").

Port-to-bit mapping uses the existing physToLogPort[] array populated
by /status.json, so the table is consistent with the icon view in
fetchVLAN() and works on any supported machine.

Each row has a delete button that sends "vlan N d" via /cmd, with
a confirmation dialog. VLAN 1 cannot be deleted (no button shown).

Table and dropdown both refresh automatically after Update/Create
and after delete via a new refreshVlanViews() helper.

The N+1 request pattern (1x /vlanlist + Nx /vlan.json) keeps the
backend simple and avoids buffer overflow risks for systems with
many VLANs. For typical configurations (<50 VLANs), page load
remains under one second.

html/vlan.js

@@ -83,6 +83,95 @@ function fetchVLAN() {
   sendXHTTP(xhttp);
 }
 
+function portsToRange(mask, nPorts) {
+  var parts = [];
+  var start = -1, prev = -1;
+  for (var p = 1; p <= nPorts; p++) {
+    var bit = physToLogPort[p - 1];
+    if ((mask >> bit) & 1) {
+      if (start < 0) start = p;
+      prev = p;
+    } else {
+      if (start >= 0) {
+        parts.push(start === prev ? String(start) : start + '-' + prev);
+        start = -1; prev = -1;
+      }
+    }
+  }
+  if (start >= 0)
+    parts.push(start === prev ? String(start) : start + '-' + prev);
+  return parts.length ? parts.join(',') : '-';
+}
+
+async function loadVlanTable() {
+  var tbody = document.getElementById('vlanTableBody');
+  if (!tbody) return;
+  tbody.innerHTML = '';
+  var resp;
+  try { resp = await fetch('/vlanlist'); } catch(e) { return; }
+  if (!resp.ok) return;
+  var vlans = await resp.json();
+  for (var i = 0; i < vlans.length; i++) {
+    var v = vlans[i];
+    var vresp;
+    try { vresp = await fetch('/vlan.json?vid=' + v.id); } catch(e) { continue; }
+    if (!vresp.ok) continue;
+    var s = await vresp.json();
+    var m = parseInt(s.members, 16);
+    var members = m & 0x3FF;
+    var untag   = (m >> 10) & 0x3FF;
+    var tagged  = members & ~untag;
+    var pvid    = parseInt(s.pvid, 16) & 0x3FF;
+    var tr = document.createElement('tr');
+    var td, a, btn;
+    td = document.createElement('td');
+    a = document.createElement('a');
+    a.href = '#';
+    a.textContent = v.id;
+    (function(vid) {
+      a.onclick = function(e) {
+        e.preventDefault();
+        document.getElementById('vid').value = vid;
+        fetchVLAN();
+      };
+    })(v.id);
+    td.appendChild(a); tr.appendChild(td);
+    td = document.createElement('td');
+    td.textContent = v.name || ''; tr.appendChild(td);
+    td = document.createElement('td');
+    td.textContent = portsToRange(members, numPorts); tr.appendChild(td);
+    td = document.createElement('td');
+    td.textContent = portsToRange(tagged, numPorts); tr.appendChild(td);
+    td = document.createElement('td');
+    td.textContent = portsToRange(untag, numPorts); tr.appendChild(td);
+    td = document.createElement('td');
+    td.textContent = portsToRange(pvid, numPorts); tr.appendChild(td);
+    td = document.createElement('td');
+    if (v.id !== 1) {
+      btn = document.createElement('button');
+      btn.textContent = '✕';
+      (function(vid) {
+        btn.onclick = function() { deleteVlan(vid); };
+      })(v.id);
+      td.appendChild(btn);
+    }
+    tr.appendChild(td);
+    tbody.appendChild(tr);
+  }
+}
+
+function deleteVlan(id) {
+  if (!confirm('Delete VLAN ' + id + '?')) return;
+  fetch('/cmd', { method: 'POST', body: 'vlan ' + id + ' d' })
+    .then(function() { refreshVlanViews(); })
+    .catch(function(err) { console.error('Delete failed:', err); });
+}
+
+function refreshVlanViews() {
+  loadVlanList();
+  loadVlanTable();
+}
+
 function loadVlanList() {
   var xhttp = new XMLHttpRequest();
   xhttp.onreadystatechange = function() {
@@ -112,7 +201,7 @@ function loadVlanList() {
 window.addEventListener("load", function() {
   update( () => {
     vlanForm();
-    loadVlanList();
+    refreshVlanViews();
     document.getElementById('vlanSelect').onchange = function() {
       document.getElementById('vid').value = this.value;
       fetchVLAN();