feat: add integration tests and runnable examples

Add 91 integration tests (all #[ignore]) mirroring the JavaScript SDK's
integration test suite. Tests cover all endpoints: ping, apps, fields,
records, files, lists, and reports with success, auth, access, and
not-found scenarios.

Add 7 runnable examples (cargo run --example <name>) for quick manual
smoke testing against a real Onspring instance.

Both use env vars (API_BASE_URL, SANDBOX_API_KEY, TEST_*) matching the
JavaScript SDK setup.

Also rename crate to onspring-api-sdk-rust with [lib] name = "onspring"
so imports remain `use onspring::*`.

tests/integration_lists.rs

@@ -0,0 +1,166 @@
+mod integration_common;
+
+use integration_common::*;
+use onspring::SaveListItemRequest;
+
+#[tokio::test]
+#[ignore]
+async fn save_list_item_should_add_item() {
+  let client = build_client();
+  let list_id = required_env_i32("TEST_LIST_ID");
+
+  let name = format!("added_list_value_{}", chrono::Utc::now().timestamp_millis());
+  let request = SaveListItemRequest {
+    id: None,
+    name,
+    numeric_value: Some(1.0),
+    color: Some("#000000".to_string()),
+  };
+
+  let response = client.save_list_item(list_id, request).await.unwrap();
+  let item_id = response.id;
+
+  // Cleanup
+  let _ = client.delete_list_item(list_id, item_id).await;
+}
+
+#[tokio::test]
+#[ignore]
+async fn save_list_item_should_update_item() {
+  let client = build_client();
+  let list_id = required_env_i32("TEST_LIST_ID");
+
+  // Create
+  let name = format!("added_list_value_{}", chrono::Utc::now().timestamp_millis());
+  let request = SaveListItemRequest {
+    id: None,
+    name,
+    numeric_value: None,
+    color: None,
+  };
+  let created = client.save_list_item(list_id, request).await.unwrap();
+
+  // Update
+  let name = format!(
+    "updated_list_value_{}",
+    chrono::Utc::now().timestamp_millis()
+  );
+  let update_request = SaveListItemRequest {
+    id: Some(created.id),
+    name,
+    numeric_value: Some(1.0),
+    color: Some("#000000".to_string()),
+  };
+  let _response = client
+    .save_list_item(list_id, update_request)
+    .await
+    .unwrap();
+
+  // Cleanup
+  let _ = client.delete_list_item(list_id, created.id).await;
+}
+
+#[tokio::test]
+#[ignore]
+async fn save_list_item_should_fail_with_invalid_api_key() {
+  let client = build_client_with_key("invalid");
+  let request = SaveListItemRequest {
+    id: None,
+    name: "test".to_string(),
+    numeric_value: Some(1.0),
+    color: Some("#000000".to_string()),
+  };
+  let result = client.save_list_item(1, request).await;
+  assert!(result.is_err());
+}
+
+#[tokio::test]
+#[ignore]
+async fn save_list_item_should_fail_when_list_not_found() {
+  let client = build_client();
+  let request = SaveListItemRequest {
+    id: None,
+    name: "test".to_string(),
+    numeric_value: Some(1.0),
+    color: Some("#000000".to_string()),
+  };
+  let result = client.save_list_item(0, request).await;
+  assert!(result.is_err());
+}
+
+#[tokio::test]
+#[ignore]
+async fn save_list_item_should_fail_when_item_not_found() {
+  let client = build_client();
+  let list_id = required_env_i32("TEST_LIST_ID");
+  let fake_uuid = uuid::Uuid::parse_str("3fa85f64-5717-4562-b3fc-2c963f66afa6").unwrap();
+
+  let request = SaveListItemRequest {
+    id: Some(fake_uuid),
+    name: "test".to_string(),
+    numeric_value: Some(1.0),
+    color: Some("#000000".to_string()),
+  };
+  let result = client.save_list_item(list_id, request).await;
+  assert!(result.is_err());
+}
+
+#[tokio::test]
+#[ignore]
+async fn delete_list_item_should_succeed() {
+  let client = build_client();
+  let list_id = required_env_i32("TEST_LIST_ID");
+
+  // Create first
+  let name = format!("to_delete_{}", chrono::Utc::now().timestamp_millis());
+  let request = SaveListItemRequest {
+    id: None,
+    name,
+    numeric_value: Some(1.0),
+    color: Some("#000000".to_string()),
+  };
+  let created = client.save_list_item(list_id, request).await.unwrap();
+
+  // Delete
+  client.delete_list_item(list_id, created.id).await.unwrap();
+}
+
+#[tokio::test]
+#[ignore]
+async fn delete_list_item_should_fail_with_invalid_api_key() {
+  let client = build_client_with_key("invalid");
+  let fake_uuid = uuid::Uuid::parse_str("3fa85f64-5717-4562-b3fc-2c963f66afa6").unwrap();
+  let result = client.delete_list_item(1, fake_uuid).await;
+  assert!(result.is_err());
+}
+
+#[tokio::test]
+#[ignore]
+async fn delete_list_item_should_fail_when_no_access() {
+  let client = build_client();
+  let list_id = required_env_i32("TEST_LIST_ID_NO_ACCESS");
+  let item_id = required_env("TEST_LIST_ITEM_ID_NO_ACCESS");
+  let uuid = uuid::Uuid::parse_str(&item_id).unwrap();
+
+  let result = client.delete_list_item(list_id, uuid).await;
+  assert!(result.is_err());
+}
+
+#[tokio::test]
+#[ignore]
+async fn delete_list_item_should_fail_when_list_not_found() {
+  let client = build_client();
+  let fake_uuid = uuid::Uuid::parse_str("3fa85f64-5717-4562-b3fc-2c963f66afa6").unwrap();
+  let result = client.delete_list_item(0, fake_uuid).await;
+  assert!(result.is_err());
+}
+
+#[tokio::test]
+#[ignore]
+async fn delete_list_item_should_fail_when_item_not_found() {
+  let client = build_client();
+  let list_id = required_env_i32("TEST_LIST_ID");
+  let fake_uuid = uuid::Uuid::parse_str("3fa85f64-5717-4562-b3fc-2c963f66afa6").unwrap();
+  let result = client.delete_list_item(list_id, fake_uuid).await;
+  assert!(result.is_err());
+}