add iterators

New iterators can be used to iterate through Nodes.

Squashed commit of the following:

commit 602ed679631647dd1c8874b0b0145fcb09458341
Author: GRayHook <s@marinkevich.ru>
Date:   Fri Aug 1 19:36:46 2025 +0700

    fup after CR

commit 08f7b59aa7
Author: GRayHook <s@marinkevich.ru>
Date:   Fri Aug 1 19:20:48 2025 +0700

    normalize members of iterator

commit 038cbb73f4
Author: GRayHook <s@marinkevich.ru>
Date:   Fri Aug 1 18:57:08 2025 +0700

    bump

commit 0f93988fb6
Author: GRayHook <s@marinkevich.ru>
Date:   Fri Aug 1 11:32:35 2025 +0700

    tmp

include/ifaces/IIterator.h

@@ -0,0 +1,14 @@
+#pragma once
+
+/// \brief Интерфейс для классов-итераторов.
+/// \tparam T Тип итерируемого элемента.
+template <typename T>
+class IIterator {
+public:
+	virtual T* operator->() const = 0;
+	virtual operator const T*() const = 0;
+
+	virtual bool operator!=(const IIterator& other) const = 0;
+
+	virtual IIterator& operator++() = 0;
+};

include/ifaces/ILinkMixin.h

@@ -14,5 +14,6 @@ public:
 	virtual void linkChild(const ElemPtr& child) = 0;
 	virtual void unlinkParent() = 0;
 	virtual const std::vector<ElemPtr>& children() = 0;
+	virtual ElemPtr parent() = 0;
 	virtual LinkPtr getLink() = 0;
 };