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/ScenariosPage.tsx

@@ -1,7 +1,7 @@
 import { useCallback, useEffect, useRef, useState } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { useTranslation } from 'react-i18next';
-import { Play, Plus, Trash2, Download } from 'lucide-react';
+import { Play, Plus, Trash2, Download, ClipboardList } from 'lucide-react';
 import { parse as yamlParse } from 'yaml';
 import { scenarios } from '../../api';
 import type { Scenario } from '../../api';
@@ -89,7 +89,7 @@ export function ScenariosPage() {
   return (
     <div>
       <div className={styles.pageToolbar}>
-        <Breadcrumbs items={[{ label: t('scenarios.title') }]} className={styles.breadcrumbs} />
+        <Breadcrumbs items={[{ label: t('scenarios.title'), icon: <ClipboardList size={14} /> }]} />
         <div className={styles.toolbarActions}>
           <input
             ref={fileInputRef}