feat(ui): admin page for outbound connections list + navigation

Adds OutboundConnectionsPage (list view with delete), lazy route at
/admin/outbound-connections, and Outbound Connections nav node in the
admin sidebar tree. No test file created — UI codebase has no existing
test infrastructure to build on.

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

ui/src/components/sidebar-utils.ts

@@ -107,6 +107,7 @@ export function buildAdminTreeNodes(opts?: { infrastructureEndpoints?: boolean }
     ...(showInfra ? [{ id: 'admin:database', label: 'Database', path: '/admin/database' }] : []),
     { id: 'admin:environments', label: 'Environments', path: '/admin/environments' },
     { id: 'admin:oidc', label: 'OIDC', path: '/admin/oidc' },
+    { id: 'admin:outbound-connections', label: 'Outbound Connections', path: '/admin/outbound-connections' },
     { id: 'admin:sensitive-keys', label: 'Sensitive Keys', path: '/admin/sensitive-keys' },
     { id: 'admin:rbac', label: 'Users & Roles', path: '/admin/rbac' },
   ];