fix: scroll to reply anchor on forum topic page

When opening a forum topic from a notification link (e.g. #reply-55),
the page now smoothly scrolls to the specific reply with a brief
highlight, accounting for the sticky header offset.

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

templates/forum/topic.html

@@ -1503,6 +1503,25 @@
 {% endblock %}
 
 {% block extra_js %}
+    // Scroll to reply anchor (e.g. from notification link #reply-55)
+    (function() {
+        var hash = window.location.hash;
+        if (hash && hash.startsWith('#reply-')) {
+            var target = document.getElementById(hash.substring(1));
+            if (target) {
+                var headerH = document.querySelector('header');
+                var offset = headerH ? headerH.offsetHeight + 16 : 80;
+                setTimeout(function() {
+                    var top = target.getBoundingClientRect().top + window.pageYOffset - offset;
+                    window.scrollTo({ top: top, behavior: 'smooth' });
+                    target.style.transition = 'box-shadow 0.3s ease';
+                    target.style.boxShadow = '0 0 0 3px var(--primary-light, #4a6999)';
+                    setTimeout(function() { target.style.boxShadow = ''; }, 3000);
+                }, 200);
+            }
+        }
+    })();
+
     function showToast(message, type = 'info', duration = 4000) {
         const container = document.getElementById('toastContainer');
         const icons = { success: '✓', error: '✕', warning: '⚠', info: 'ℹ' };