fix(admin-panel): inline skeleton loaders for table sections (#20014)

## Summary
\`SettingsSkeletonLoader\` wraps its content in \`PageHeader\` +
\`PageBody\`, which is right for **full-page replacement** (user detail,
config variable detail, etc.) but renders as a large empty stub with one
tiny floating bar when placed **inline inside a section that's already
scaffolded**. That's what showed up in Recent Users, Top Workspaces, and
the Chats tab in the admin panel — a jarring white page flash where a
few row placeholders should be.

This PR adds \`SettingsAdminSectionSkeletonLoader\` — a small,
configurable-row-count skeleton that uses the project's standard
\`SkeletonTheme\` pattern (\`theme.background.tertiary\` /
\`theme.background.transparent.lighter\` + \`borderRadius: 4\`, matching
\`PageContentSkeletonLoader\` and \`SettingsAdminTabSkeletonLoader\`)
and renders row-height bars that match \`TableRow\` spacing. Swaps it
into the three inline call sites.

Full-page usages of \`SettingsSkeletonLoader\` are unchanged.

### Changed
- **New**:
\`packages/twenty-front/src/modules/settings/admin-panel/components/SettingsAdminSectionSkeletonLoader.tsx\`
- **Swapped** (3 inline loading states): \`SettingsAdminGeneral.tsx\`
(Recent Users + Top Workspaces), \`SettingsAdminWorkspaceDetail.tsx\`
(Chats tab)

## Test plan
- [x] typecheck (\`npx nx typecheck twenty-front --skip-nx-cache\`) —
clean
- [x] oxlint — 0 warnings
- [x] prettier — clean
- [ ] Visual: navigate to admin panel, observe Recent Users / Top
Workspaces / Chats tab loading — should see a tight stack of row-height
placeholder bars instead of a big empty page stub

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/twenty-front/src/modules/settings/admin-panel/config-variables/components/SettingsAdminConfigVariables.tsx

@@ -1,4 +1,4 @@
-import { SettingsAdminTabSkeletonLoader } from '@/settings/admin-panel/components/SettingsAdminTabSkeletonLoader';
+import { SettingsSectionSkeletonLoader } from '@/settings/components/SettingsSectionSkeletonLoader';
 import { useApolloAdminClient } from '@/settings/admin-panel/apollo/hooks/useApolloAdminClient';
 import { ConfigVariableFilterContainer } from '@/settings/admin-panel/config-variables/components/ConfigVariableFilterContainer';
 import { ConfigVariableFilterDropdown } from '@/settings/admin-panel/config-variables/components/ConfigVariableFilterDropdown';
@@ -160,7 +160,7 @@ export const SettingsAdminConfigVariables = () => {
   }, [filteredVariables, allGroups]);
 
   if (configVariablesLoading) {
-    return <SettingsAdminTabSkeletonLoader />;
+    return <SettingsSectionSkeletonLoader />;
   }
 
   return (