Fix avatar color drift between PHP and JS (#31)

The JS side claimed to "mirror the PHP crc32 % 4 logic" but actually
implemented a different rolling hash (classic String.hashCode()-style),
so the same display name could get different avatar colors depending
on whether a comment was server-rendered or client-rendered (new
comment, reply, watcher avatars, "Load more" pagination).

Added a real CRC-32 (IEEE 802.3/zlib polynomial, UTF-8 byte sequence)
to ticket.js and switched all three JS call sites (avatarColorClass,
watcher avatars, and buildCommentEl in TicketView.php) to use it,
verified to produce identical output to PHP's crc32() including for
non-ASCII names.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MGDKHiU5RJdo3dqQUDow3X

assets/js/ticket.js

@@ -183,15 +183,35 @@ function toggleEditMode() {
 }
 
 /**
- * Compute avatar color class from display name (mirrors PHP crc32 % 4 logic)
+ * CRC-32 (IEEE 802.3 / zlib polynomial), matching PHP's crc32(). Operates on
+ * the UTF-8 byte sequence, same as PHP, so results agree for non-ASCII names.
+ */
+function crc32(str) {
+    var bytes = unescape(encodeURIComponent(str));
+    var table = crc32._table || (crc32._table = (function () {
+        var t = [];
+        for (var n = 0; n < 256; n++) {
+            var c = n;
+            for (var k = 0; k < 8; k++) {
+                c = (c & 1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1);
+            }
+            t[n] = c;
+        }
+        return t;
+    })());
+    var crc = -1;
+    for (var i = 0; i < bytes.length; i++) {
+        crc = (crc >>> 8) ^ table[(crc ^ bytes.charCodeAt(i)) & 0xFF];
+    }
+    return (crc ^ -1) >>> 0;
+}
+
+/**
+ * Compute avatar color class from display name (mirrors PHP's crc32 % 4 logic)
  */
 function avatarColorClass(displayName) {
     var colors = ['lt-avatar--orange', 'lt-avatar--green', 'lt-avatar--purple', ''];
-    var h = 0;
-    for (var i = 0; i < displayName.length; i++) {
-        h = ((h << 5) - h + displayName.charCodeAt(i)) | 0;
-    }
-    return colors[Math.abs(h) % 4];
+    return colors[crc32(displayName) % 4];
 }
 
 /**