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/static/common.js

@@ -0,0 +1,30 @@
+'use strict';
+const $ = s => document.querySelector(s);
+function wsURL(path){ return (location.protocol === 'https:' ? 'wss://' : 'ws://') + location.host + path; }
+function fmtTime(ts){ const d = new Date(ts); return d.toLocaleTimeString([], {hour:'2-digit', minute:'2-digit'}); }
+// Render a chat message. `mine` = which side this page is ('host' | 'guest'). Text only - never innerHTML.
+function renderMsg(log, m, mine){
+  const el = document.createElement('div');
+  el.className = 'msg ' + (m.who === 'system' ? 'system' : (m.who === mine ? 'me' : 'them'));
+  if (m.who !== 'system') {
+    const w = document.createElement('span'); w.className = 'who';
+    w.textContent = (m.who === mine ? 'You' : m.from) + ' · ' + fmtTime(m.ts);
+    el.appendChild(w);
+  }
+  el.appendChild(document.createTextNode(m.text));
+  const atBottom = log.scrollHeight - log.scrollTop - log.clientHeight < 40;
+  log.appendChild(el);
+  if (atBottom || m.who === mine) log.scrollTop = log.scrollHeight;
+}
+function setMeter(el, peak){ // peak 0..1 linear -> bar on a -60..0 dBFS scale
+  const db = peak > 0 ? 20*Math.log10(peak) : -100;
+  const pct = Math.max(0, Math.min(100, (db + 60) / 60 * 100));
+  el.style.width = pct + '%';
+  el.className = db > -1 ? 'clip' : (db > -9 ? 'hot' : '');
+  return db;
+}
+function chatForm(form, ta, send){
+  form.addEventListener('submit', e => { e.preventDefault(); const t = ta.value.trim(); if (t) { send(t); ta.value=''; } ta.focus(); });
+  ta.addEventListener('keydown', e => { if (e.key === 'Enter' && !e.shiftKey && !e.isComposing) { e.preventDefault(); form.requestSubmit(); } });
+}
+function store(k, v){ try { if (v === undefined) return localStorage.getItem(k); localStorage.setItem(k, v); } catch(e) { return null; } }