feat: 人设模板系统、节点调度标签、pydantic-settings收敛、错误处理增强

新增persona_template表和CRUD API，BaseIndividualModel增加node_affinity和template_origin_id字段，
WorkerCluster支持多集群Ray资源调度，环境变量收敛到pydantic-settings统一校验，
数据库异常转换为结构化BusinessError/RetryableError，系统节点支持custom_system_prompt。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

kilostar/utils/ray_hook.py

@@ -125,3 +125,18 @@ def ray_actor_hook(*actor_names: str, timeout: float = 0.0, interval: float = 0.
             handle = _get_cached_actor_handle(actor_name)
         setattr(actor_list, actor_name, handle)
     return actor_list
+
+
+def get_worker_cluster(affinity: str = "cpu"):
+    """按 node_affinity 标签取对应的 WorkerCluster actor 句柄。
+
+    单机模式统一返回唯一的 worker_cluster 实例。
+    分布式模式按 affinity 路由到 worker_cluster_cpu / _core / _gpu。
+    未知标签降级到 cpu。
+    """
+    if _STANDALONE:
+        return _standalone_registry.get("worker_cluster")
+
+    _valid = {"cpu", "core", "gpu"}
+    node_type = affinity if affinity in _valid else "cpu"
+    return _get_cached_actor_handle(f"worker_cluster_{node_type}")