chore: initial baseline with P0-safety .gitignore

docs/diagrams/admin-config-change-sequence.mermaid

@@ -0,0 +1,19 @@
+sequenceDiagram
+    participant U as 管理员
+    participant FE as frontend-admin
+    participant API as /api/admin/configs/{key}
+    participant SVC as admin_service
+    participant DB as PostgreSQL
+
+    U->>FE: 切换应急模式开关
+    FE->>API: PUT /api/admin/configs/emergency_mode
+    API->>API: require_admin 校验权限
+    API->>SVC: update_config(key, value, agent_id)
+    SVC->>DB: SELECT SystemConfig WHERE key=emergency_mode
+    DB-->>SVC: 当前值 "false"
+    SVC->>DB: INSERT ConfigChangeLog(old="false", new="true", by=agent_id)
+    SVC->>DB: UPDATE SystemConfig SET value="true"
+    DB-->>SVC: 更新成功
+    SVC-->>API: {key, old_value, new_value, changed_at}
+    API-->>FE: 返回变更结果
+    FE->>FE: 显示变更成功提示