feat(ui): replace Switch with TogglePill per design audit (#687)

* chore: ignore local design-system references

Adds frontend/DESIGN.md and .design-bundle/ to .gitignore so the
design-system reference and the audit handoff bundle stay local
to each contributor's machine.

* feat(ui): replace Switch with TogglePill per design audit

Adds a mono-uppercase ON/OFF pill that replaces the sliding Switch
across every call site. The pill uses role="switch" plus aria-checked,
tints success-green when on and neutral card-tone when off, and holds
a stable 60px min-width so the label flip does not shift layout. It
reinforces the tracked-mono uppercase pattern already used for kicker
labels and table column headers, and echoes the UP/DN status language
of the sidebar stack list.

- Add TogglePill component (frontend/src/components/ui/toggle-pill.tsx)
- Replace 17 Switch call sites across 10 files (settings sections,
  SSO providers, scheduled operations, network topology, resources,
  stack auto-heal)
- Remove unused Switch wrapper and radix primitive
- Drop the @radix-ui/react-switch dependency

frontend/src/components/NetworkTopologyView.tsx

@@ -18,7 +18,7 @@ import { apiFetch } from '@/lib/api';
 import { toast } from '@/components/ui/toast-store';
 import { Container, Network, Loader2, RefreshCw } from 'lucide-react';
 import { Badge } from '@/components/ui/badge';
-import { Switch } from '@/components/ui/switch';
+import { TogglePill } from '@/components/ui/toggle-pill';
 import { Label } from '@/components/ui/label';
 import { Button } from '@/components/ui/button';
 import { cn } from '@/lib/utils';
@@ -306,7 +306,7 @@ export default function NetworkTopologyView({ onContainerClick }: NetworkTopolog
     return (
         <div className="rounded-lg border border-card-border bg-card shadow-card-bevel overflow-hidden">
             <div className="flex items-center gap-2 px-3 py-2 border-b border-card-border">
-                <Switch id="show-system" checked={includeSystem} onCheckedChange={setIncludeSystem} />
+                <TogglePill id="show-system" checked={includeSystem} onChange={setIncludeSystem} />
                 <Label htmlFor="show-system" className="text-xs cursor-pointer">
                     Show system networks
                 </Label>