v1.8.12: fix Ctrl+Z undo — manual implementation for tk.Entry

tk.Entry has no built-in undo (unlike tk.Text), so _entry.config(undo=True)
crashed. Replaced with custom entry_undo.py that tracks history manually
and binds Ctrl+Z/Ctrl+Y (+ Russian layout support).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

gui/widgets/entry_undo.py

@@ -0,0 +1,54 @@
+"""
+Ctrl+Z / Ctrl+Y undo/redo for CTkEntry widgets.
+tk.Entry has no built-in undo, so we track history manually.
+"""
+
+
+def enable_undo(ctk_entry):
+    """Add Ctrl+Z undo and Ctrl+Y redo to a CTkEntry widget."""
+    entry = ctk_entry._entry
+    history = [entry.get()]
+    redo_stack = []
+    _recording = [True]
+
+    def _snapshot(*_args):
+        if not _recording[0]:
+            return
+        val = entry.get()
+        if not history or history[-1] != val:
+            history.append(val)
+            redo_stack.clear()
+            # Cap history size
+            if len(history) > 200:
+                del history[:100]
+
+    def _undo(event):
+        if len(history) > 1:
+            redo_stack.append(history.pop())
+            _recording[0] = False
+            entry.delete(0, "end")
+            entry.insert(0, history[-1])
+            _recording[0] = True
+        elif history:
+            redo_stack.append(history.pop())
+            _recording[0] = False
+            entry.delete(0, "end")
+            _recording[0] = True
+        return "break"
+
+    def _redo(event):
+        if redo_stack:
+            val = redo_stack.pop()
+            history.append(val)
+            _recording[0] = False
+            entry.delete(0, "end")
+            entry.insert(0, val)
+            _recording[0] = True
+        return "break"
+
+    entry.bind("<KeyRelease>", _snapshot, add="+")
+    entry.bind("<Control-z>", _undo)
+    entry.bind("<Control-y>", _redo)
+    # Support Russian keyboard layout (Cyrillic keycodes)
+    entry.bind("<Control-\u044f>", _undo)  # Ctrl+Я (z position on Russian layout)
+    entry.bind("<Control-\u043d>", _redo)  # Ctrl+Н (y position on Russian layout)