uebung_03: implement Task 3 (BST) and Task 4 (IntHashSet)

Task 3 adds IntBinarySearchTree with iterative add/contains and a
test class covering empty trees, duplicates, and degenerate ascending
and descending insertion orders.

Task 4 adds IntHashSet backed by an IntLinkedList bucket array with
a 0.7 load factor, Math.floorMod-based hashing for negative-int
safety, doubling resize that rehashes via a private
addWithoutResize helper, and a test class covering negatives,
Integer.MIN_VALUE, forced collisions on bucket 0, and 100-element
inserts spanning three resizes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

uebung_03/src/IntTreeNode.java

@@ -0,0 +1,12 @@
+public class IntTreeNode {
+    int value;
+    IntTreeNode left;
+
+    IntTreeNode right;
+
+    public IntTreeNode(int value){
+        this.value = value;
+    }
+
+
+}