feat(ui): add breadcrumb icons, fix alignment, and remove duplicate form headers

- add section icons to all breadcrumbs across every page
- fix breadcrumb nav display:flex so icons align vertically with buttons
- wrap all page breadcrumbs in pageToolbar div for consistent layout
- add Breadcrumbs to AllRunsPage which previously used a plain h1
- fix envCardHeader flex:1 so settings button hugs the right edge
- remove card header from environment create/edit forms (duplicated breadcrumb)

client/src/pages/scenario/CreateScenarioPage.tsx

@@ -1,6 +1,7 @@
 import { useState } 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 } from '../../ui';
 import styles from '../Page.module.css';
@@ -37,7 +38,7 @@ export function CreateScenarioPage() {
       <div className={styles.pageToolbar}>
         <Breadcrumbs
           items={[
-            { label: t('scenarios.title'), onClick: () => navigate('/scenarios') },
+            { label: t('scenarios.title'), icon: <ClipboardList size={14} />, onClick: () => navigate('/scenarios') },
             { label: t('scenarios.create_title') },
           ]}
         />
@@ -64,9 +65,11 @@ export function CreateScenarioPage() {
 
           <div className={styles.formActions}>
             <Button type="button" variant="secondary" onClick={() => navigate('/scenarios')}>
+              <X size={14} />
               {t('scenarios.action_cancel')}
             </Button>
             <Button type="submit" loading={saving}>
+              <Save size={14} />
               {t('scenarios.action_save')}
             </Button>
           </div>