optimized avatar and linkify performance, refined navigation to preserve popups, implemented read marker caching, and added file size limits for saving, minor timetable details changes

lib/view/pages/talk/widgets/highlighted_linkify.dart

@@ -78,22 +78,48 @@ class HighlightedLinkify extends StatefulWidget {
 }
 
 class _HighlightedLinkifyState extends State<HighlightedLinkify> {
-  final List<TapGestureRecognizer> _recognizers = [];
+  // Cached per link text so character-by-character search rebuilds don't
+  // churn through allocate/dispose on every keystroke. Stale entries are
+  // pruned at the end of each build via [_seenLinkKeys].
+  final Map<String, TapGestureRecognizer> _recognizers = {};
+  final Set<String> _seenLinkKeys = {};
 
   @override
   void dispose() {
-    for (final r in _recognizers) {
+    for (final r in _recognizers.values) {
       r.dispose();
     }
+    _recognizers.clear();
     super.dispose();
   }
 
+  TapGestureRecognizer _recognizerFor(LinkableElement el) {
+    final key = el.text;
+    final existing = _recognizers[key];
+    if (existing != null) {
+      // Refresh onTap so a new widget.onOpen callback (from a parent
+      // rebuild) picks up the latest closure.
+      existing.onTap = () => widget.onOpen?.call(el);
+      return existing;
+    }
+    final created = TapGestureRecognizer()
+      ..onTap = () => widget.onOpen?.call(el);
+    _recognizers[key] = created;
+    return created;
+  }
+
+  void _pruneUnseen() {
+    final stale = _recognizers.keys
+        .where((k) => !_seenLinkKeys.contains(k))
+        .toList(growable: false);
+    for (final k in stale) {
+      _recognizers.remove(k)?.dispose();
+    }
+  }
+
   @override
   Widget build(BuildContext context) {
-    for (final r in _recognizers) {
-      r.dispose();
-    }
-    _recognizers.clear();
+    _seenLinkKeys.clear();
 
     final defaultStyle = widget.style ??
         Theme.of(context).textTheme.bodyMedium ??
@@ -124,9 +150,8 @@ class _HighlightedLinkifyState extends State<HighlightedLinkify> {
 
     for (final el in elements) {
       if (el is LinkableElement) {
-        final recognizer = TapGestureRecognizer()
-          ..onTap = () => widget.onOpen?.call(el);
-        _recognizers.add(recognizer);
+        _seenLinkKeys.add(el.text);
+        final recognizer = _recognizerFor(el);
         spans.addAll(
           buildHighlightedSpans(
             text: el.text,
@@ -147,6 +172,8 @@ class _HighlightedLinkifyState extends State<HighlightedLinkify> {
       }
     }
 
+    _pruneUnseen();
+
     return Text.rich(TextSpan(children: spans));
   }
 }