Batch update tags for multiple nodes

Add and/or remove tags for multiple nodes in a single atomic operation. Returns 204 No Content on success. Fails if all nodes are invalid. Tag Validation Rules (applies to tags being added): - Format: lowercase letters (a-z), numbers (0-9), hyphens (-), and underscores (_) - Must start and end with alphanumeric characters - Separators (hyphen, underscore) cannot be consecutive - Maximum length: 50 characters - Reserved names: null, none, undefined, true, false - Examples: "gpu-health", "test_tag", "node123" Note: Tags being removed are not validated, allowing removal of invalid legacy tags.