feat: tree-structure-compose (LazyTree) + O(n) addChild cycle check

- New published module tree-structure-compose: a LazyTree composable for Compose
  Multiplatform (JVM/desktop, iOS, Wasm) with lazy rendering and expand/collapse.
- Fix an O(n^2) regression in addChild(): only walk ancestors for cycle detection
  when the child already has a subtree (a fresh leaf can never form a cycle), so
  building deep trees is O(n) again. Caught by the deep-chain stack-safety test on JS.
- README: Compose usage section; align all install snippets to 4.0.0.
- Version catalog: Compose Multiplatform + compose-compiler plugins.

Verified locally: JVM, JS(node), Wasm(node), iOS-simulator tests + apiCheck all green;
Compose module compiles for JVM, Wasm and iOS.

tree-structure-compose/build.gradle.kts

@@ -0,0 +1,74 @@
+import org.jetbrains.kotlin.gradle.ExperimentalWasmDsl
+
+plugins {
+    alias(libs.plugins.kotlinMultiplatform)
+    alias(libs.plugins.composeMultiplatform)
+    alias(libs.plugins.composeCompiler)
+    alias(libs.plugins.dokka)
+    alias(libs.plugins.mavenPublish)
+    signing
+}
+
+group = "com.github.adriankuta"
+version = rootProject.version
+
+mavenPublishing {
+    publishToMavenCentral(automaticRelease = false)
+    signAllPublications()
+
+    coordinates("com.github.adriankuta", "tree-structure-compose", version.toString())
+
+    pom {
+        name.set("Tree Data Structure — Compose Multiplatform")
+        description.set("A LazyTree composable (expand/collapse, lazy rendering) for the tree-structure library.")
+        url.set("https://github.com/AdrianKuta/Tree-Data-Structure")
+        licenses {
+            license {
+                name.set("MIT License")
+                url.set("https://opensource.org/licenses/MIT")
+                distribution.set("repo")
+            }
+        }
+        developers {
+            developer {
+                id.set("AdrianKuta")
+                name.set("Adrian Kuta")
+                email.set("adrian.kuta93@gmail.com")
+            }
+        }
+        scm {
+            url.set("https://github.com/AdrianKuta/Tree-Data-Structure")
+            connection.set("scm:git:https://github.com/AdrianKuta/Tree-Data-Structure.git")
+            developerConnection.set("scm:git:ssh://git@github.com/AdrianKuta/Tree-Data-Structure.git")
+        }
+    }
+}
+
+repositories {
+    mavenCentral()
+    google()
+}
+
+kotlin {
+    explicitApi()
+    jvmToolchain(21)
+
+    jvm()
+
+    @OptIn(ExperimentalWasmDsl::class)
+    wasmJs {
+        browser()
+    }
+
+    iosX64()
+    iosArm64()
+    iosSimulatorArm64()
+
+    sourceSets {
+        commonMain.dependencies {
+            api(project(":"))
+            implementation(compose.runtime)
+            implementation(compose.foundation)
+        }
+    }
+}