Web UI: hide the VLAN split option until it is implemented

The firmware doesn't apply the VLAN split yet (phase 2). The checkbox is
hidden, which also keeps the internet-interface fields and "Web UI / API on"
hidden; the markup stays for phase 2.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -73,7 +73,7 @@ Repo: https://gitea.apointless.space/bsncubed/aes67-ESP32-P4
 - [ ] 8. Mono sum, gain, polish.
 
 ## Phase 2 (parked)
-- [ ] VLAN split: AES67 untagged + internet tagged (inet.vlan_id/pcp), per aes67-core-base.md "Network". Needs a tagged VLAN with DHCP on the switch port. Config group `inet` and the UI fields exist already; nothing is applied yet.
+- [ ] VLAN split: AES67 untagged + internet tagged (inet.vlan_id/pcp), per aes67-core-base.md "Network". Needs a tagged VLAN with DHCP on the switch port. Config group `inet` and the UI fields exist already; nothing is applied yet. The "VLAN split" checkbox is hidden in web/index.html (`<label hidden>`); unhide it when this is done.
 - [ ] NTP (SNTP): servers as hostnames or IPs (e.g. `pool.ntp.org`, several allowed; names resolved via DNS, re-resolved on failure). Uses: seed the PTP clock with real time before becoming GM (today it starts at 1970), syslog timestamps. Needs a `time` config group + UI fields (change doc and page together).
 
 ## Phase 3 (parked)

web/index.html

@@ -147,7 +147,8 @@ e.g. curl -X POST http://p4-aes67.local/api/player/next
 
 <fieldset><legend>Network</legend>
 <label><span>Hostname</span><input name="net.hostname"></label>
-<label><span>VLAN split</span><input name="net.vlan" type="checkbox">
+<!-- VLAN split: not implemented yet (phase 2); hidden until the firmware applies it. -->
+<label hidden><span>VLAN split</span><input name="net.vlan" type="checkbox">
   <small>off: one untagged interface for everything</small></label>
 <p id="netlbl" hidden><b>AES67 interface (untagged)</b></p>
 <label><span>DHCP</span><input name="net.dhcp" type="checkbox"></label>