feat(02-03): add Wasm auth stubs

- Keep Wasm OIDC behind explicit v2 NotImplementedError boundaries
- Add non-persistent Wasm AuthState store actual so the target compiles

composeApp/src/webMain/kotlin/dev/ulfrx/recipe/auth/OidcClient.wasmJs.kt

@@ -0,0 +1,17 @@
+@file:Suppress("EXPECT_ACTUAL_CLASSIFIERS_ARE_IN_BETA_WARNING")
+
+package dev.ulfrx.recipe.auth
+
+actual class OidcClient {
+    actual suspend fun login(): OidcResult {
+        throw NotImplementedError("Wasm OIDC: v2")
+    }
+
+    actual suspend fun refresh(authStateJson: String): OidcResult {
+        throw NotImplementedError("Wasm OIDC: v2")
+    }
+
+    actual suspend fun logout(authStateJson: String) {
+        throw NotImplementedError("Wasm OIDC: v2")
+    }
+}

composeApp/src/webMain/kotlin/dev/ulfrx/recipe/auth/SecureAuthStateStore.wasmJs.kt

@@ -0,0 +1,17 @@
+@file:Suppress("EXPECT_ACTUAL_CLASSIFIERS_ARE_IN_BETA_WARNING")
+
+package dev.ulfrx.recipe.auth
+
+actual class SecureAuthStateStore {
+    private var authStateJson: String? = null
+
+    actual fun read(): String? = authStateJson
+
+    actual fun write(authStateJson: String) {
+        this.authStateJson = authStateJson
+    }
+
+    actual fun clear() {
+        authStateJson = null
+    }
+}