guestlink v1: self-hosted guest line (Cleanfeed replacement)

Go + Pion + libopus. One guest, live audio both ways, anonymous chat.
README for this version was not preserved; see the next commit.

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

web/host.html

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+<!doctype html>
+<html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1">
+<title>Guest Line Console</title><link rel="stylesheet" href="/static/style.css"></head>
+<body>
+<header><h1>Guest Line - host console</h1><span id="conn" class="pill">connecting…</span></header>
+<main class="grid">
+  <section class="card">
+    <h2>Invite</h2>
+    <div class="row"><input id="link" readonly placeholder="No active link"><button id="copy">Copy</button></div>
+    <div class="row">
+      <button id="newlink">New link</button>
+      <button id="revoke" class="danger">Revoke link</button>
+    </div>
+    <p class="muted small">A new link ends the current session and clears chat. Old links stop working.</p>
+    <h2>Guest</h2>
+    <div id="guest" class="big">No guest connected</div>
+    <div id="callinfo" class="muted small"></div>
+    <div class="meter"><span>Guest &rarr; show</span><div class="bar"><i id="mIn"></i></div><b id="dIn"></b></div>
+    <div class="meter"><span>Mix-minus &rarr; guest</span><div class="bar"><i id="mOut"></i></div><b id="dOut"></b></div>
+    <div id="jb" class="muted small mono"></div>
+    <div class="row">
+      <button id="endcall">End audio</button>
+      <button id="kick" class="danger">Kick guest</button>
+    </div>
+  </section>
+  <section class="card chat">
+    <div class="row between"><h2>Chat</h2><button id="clear" class="small">Clear</button></div>
+    <div id="log" class="log" aria-live="polite"></div>
+    <form id="chatform" class="row"><textarea id="msg" rows="2" maxlength="2000" placeholder="Message the guest… (Enter to send)"></textarea><button class="primary">Send</button></form>
+  </section>
+</main>
+<script src="/static/common.js"></script>
+<script src="/static/host.js"></script>
+</body></html>