fix: linkify URLs in private messages

URLs in message content were rendered as plain text. Added linkifyContent()
that converts URLs to clickable links while preserving existing <a> tags.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

static/js/conversations.js

@@ -135,6 +135,30 @@
         return tmp.textContent || tmp.innerText || '';
     }
 
+    // ============================================================
+    // UTIL: linkify URLs in HTML content
+    // ============================================================
+
+    function linkifyContent(html) {
+        if (!html) return html;
+        var tmp = document.createElement('div');
+        tmp.innerHTML = html;
+        var walker = document.createTreeWalker(tmp, NodeFilter.SHOW_TEXT, null, false);
+        var textNodes = [];
+        while (walker.nextNode()) textNodes.push(walker.currentNode);
+        var urlRegex = /(https?:\/\/[^\s<>"']+)/g;
+        textNodes.forEach(function(node) {
+            if (node.parentNode && node.parentNode.tagName === 'A') return;
+            if (urlRegex.test(node.nodeValue)) {
+                var span = document.createElement('span');
+                span.innerHTML = node.nodeValue.replace(urlRegex, '<a href="$1" target="_blank" rel="noopener" style="color:inherit;text-decoration:underline;">$1</a>');
+                node.parentNode.replaceChild(span, node);
+            }
+            urlRegex.lastIndex = 0;
+        });
+        return tmp.innerHTML;
+    }
+
     // ============================================================
     // UTIL: avatar color from name hash
     // ============================================================
@@ -547,7 +571,7 @@
 
             // Content
             var content = el('div', 'message-content');
-            content.innerHTML = msg.content || '';
+            content.innerHTML = linkifyContent(msg.content || '');
 
             // Highlight search term if active
             if (state.searchHighlight) {