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/session/SessionsPage.tsx

@@ -1,7 +1,7 @@
 import { useCallback, useEffect, useState } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { useTranslation } from 'react-i18next';
-import { Trash2 } from 'lucide-react';
+import { Trash2, Monitor } from 'lucide-react';
 import { sessions } from '../../api';
 import type { Session } from '../../api';
 import {
@@ -75,7 +75,9 @@ export function SessionsPage() {
 
   return (
     <div>
-      <Breadcrumbs items={[{ label: t('sessions.title') }]} className={styles.breadcrumbs} />
+      <div className={styles.pageToolbar}>
+        <Breadcrumbs items={[{ label: t('sessions.title'), icon: <Monitor size={14} /> }]} />
+      </div>
       {error && <p className={styles.error}>{error}</p>}
       <Table
         columns={columns}