Tolerate 404 on delete operations

- delete_task returns Ok(()) on 404 (already deleted)
- delete_list returns Ok(()) on 404 (already deleted)

src/infrastructure/api.rs

@@ -393,6 +393,10 @@ impl ApiClient {
             .map_err(|e| ApiError::Network(e.to_string()))?;
 
         if !resp.status().is_success() {
+            // 404 means already deleted — treat as success
+            if resp.status() == 404 {
+                return Ok(());
+            }
             return Err(ApiError::Api(format!(
                 "Delete failed: {}",
                 resp.status()
@@ -420,6 +424,10 @@ impl ApiClient {
 
         if !resp.status().is_success() {
             let status = resp.status();
+            // 404 means already deleted — treat as success
+            if status == 404 {
+                return Ok(());
+            }
             let body = resp.text().await.unwrap_or_default();
             return Err(ApiError::Api(format!("Delete list failed: {} - {}", status, body)));
         }