feat(scenarios): link scenarios to a default environment

- add optional ManyToOne relation from scenario to environment entity
- expose environmentId in create/update DTOs, service, and MCP tools
- pre-select linked environment in run modals on detail and list pages
- add environment selector to create/edit scenario forms
- show linked environment as a navigable link on scenario detail page

client/src/pages/scenario/CreateScenarioPage.tsx

@@ -1,9 +1,10 @@
-import { useState, SubmitEvent } from 'react';
+import { useEffect, useState, SubmitEvent } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { useTranslation } from 'react-i18next';
 import { X, Save, ClipboardList } from 'lucide-react';
-import { scenarios } from '../../api';
-import { Breadcrumbs, Button, Card, Input, CodeEditor, useToast } from '../../ui';
+import { scenarios, environments } from '../../api';
+import type { Environment } from '../../api';
+import { Breadcrumbs, Button, Card, Input, CodeEditor, Select, useToast } from '../../ui';
 import styles from '../Page.module.css';
 
 export function CreateScenarioPage() {
@@ -13,9 +14,15 @@ export function CreateScenarioPage() {
 
   const [name, setName] = useState('');
   const [description, setDescription] = useState('');
+  const [environmentId, setEnvironmentId] = useState('');
+  const [envs, setEnvs] = useState<Environment[]>([]);
   const [nameError, setNameError] = useState('');
   const [saving, setSaving] = useState(false);
 
+  useEffect(() => {
+    environments.list(1, 200).then((r) => setEnvs(r?.data ?? [])).catch(() => {});
+  }, []);
+
   const handleSubmit = async (e: SubmitEvent<HTMLFormElement>) => {
     e.preventDefault();
     if (!name.trim()) {
@@ -24,7 +31,7 @@ export function CreateScenarioPage() {
     }
     setSaving(true);
     try {
-      const scenario = await scenarios.create(name.trim(), description.trim() || undefined);
+      const scenario = await scenarios.create(name.trim(), description.trim() || undefined, environmentId || undefined);
       toast.success(t('scenarios.created'));
       navigate(`/scenarios/${scenario.id}`);
     } catch (err) {
@@ -74,6 +81,15 @@ export function CreateScenarioPage() {
                 rows={8}
               />
             </div>
+            <Select
+              label={t('scenarios.form_environment')}
+              value={environmentId}
+              onChange={(e) => setEnvironmentId(e.target.value)}
+              options={[
+                { value: '', label: t('scenarios.form_environment_none') },
+                ...envs.map((env) => ({ value: env.id, label: env.name })),
+              ]}
+            />
           </div>
 
           <div className={styles.formActions}>