Get project import status

        Poll the status of an asynchronous project import operation.
        
        **Usage:**
        1. When you POST to `/api/projects/{project_id}/import`, you'll receive a response like `{"import": <import_id>}`
        2. Use that `import_id` with this GET endpoint to check the import status
        3. Poll this endpoint to see if the import has completed, is still processing, or has failed
        4. **Import errors and failures will only be visible in this GET response**, not in the original POST request
        
        This endpoint returns detailed information about the import including task counts, status, and any error messages.
        While an import is running, `task_count` / annotation / prediction counts update as batches commit.
        Counts are cumulative so far; there is no expected total, so percent-complete / ETA is not available from this API.