Add ArtNetDMX Pico W firmware with dual DMX and docs.

Art-Net to two RS-485 outputs over Wi-Fi (AP or STA with SoftAP fallback), web UI, mDNS, and QLC+/ArtPoll notes for unicast on STA.

Co-authored-by: Cursor <cursoragent@cursor.com>

www/index.html

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+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width,initial-scale=1">
+<title>ArtNetDMX</title>
+<link rel="stylesheet" href="/style.css">
+</head>
+<body>
+<header>
+  <h1>ArtNetDMX</h1>
+  <nav><a href="/" class="active">Channels</a><a href="/wifi">WiFi</a></nav>
+  <div id="status" class="status">…</div>
+</header>
+<main>
+  <div class="tabs">
+    <button type="button" id="tab0" class="active" data-u="0">Universe A</button>
+    <button type="button" id="tab1" data-u="1">Universe B</button>
+    <button type="button" id="clear">Clear</button>
+    <button type="button" id="full">All 255</button>
+  </div>
+  <div id="grid" class="grid"></div>
+</main>
+<script src="/app.js"></script>
+</body>
+</html>