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/snippet/SnippetsPage.tsx

@@ -1,7 +1,7 @@
 import { useEffect, useRef, useState } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { useTranslation } from 'react-i18next';
-import { Code, Pencil, Trash2, Plus, Download } from 'lucide-react';
+import { Code, Pencil, Trash2, Plus, Download, Braces } from 'lucide-react';
 import { parse as yamlParse } from 'yaml';
 import { snippets } from '../../api';
 import type { Snippet } from '../../api';
@@ -116,7 +116,7 @@ export function SnippetsPage() {
   return (
     <div>
       <div className={styles.pageToolbar}>
-        <Breadcrumbs items={[{ label: t('snippets.title') }]} />
+        <Breadcrumbs items={[{ label: t('snippets.title'), icon: <Braces size={14} /> }]} />
         <div className={styles.toolbarActions}>
           <input
             ref={fileInputRef}