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/api/system.py

@@ -106,3 +106,10 @@ async def query_system_logs(
         offset=offset,
     )
     return {"logs": logs, "count": len(logs)}
+
+
+@system_router.get("/api/v1/system/node-labels")
+async def get_node_labels(
+    _: TokenData = Depends(Accessor.get_current_user),
+):
+    return {"node_labels": ["cpu", "core", "gpu"]}