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/iterators/DFSIterator.h

@@ -0,0 +1,43 @@
+#pragma once
+#include <stack>
+#include <iterator>
+
+#include "iterators/BaseIterator.h"
+
+template <typename T>
+class DFSIterator : public BaseIterator<T> {
+public:
+	explicit DFSIterator(T* ptr) : BaseIterator<T>(ptr) {
+		if (!this->current())
+			return;
+
+		for (auto it = this->current()->children().rbegin();
+		     it != this->current()->children().rend(); ++it)
+			s.push({it->get(), 1});
+	}
+
+	IIterator<T>& operator++() override {
+		advance();
+		return *this;
+	}
+
+protected:
+	std::stack<std::pair<T*, size_t>> s;
+
+	void advance() {
+		if (s.empty()) {
+			this->set_current(nullptr);
+			return;
+		}
+
+		auto [node, lvl] = s.top();
+		s.pop();
+
+		this->set_current(node);
+		this->set_level(lvl);
+
+		for (auto it = this->current()->children().rbegin();
+		     it != this->current()->children().rend(); ++it)
+			s.push({it->get(), lvl + 1});
+	}
+};