feat(failover): add auto-failover master switch with proxy integration (#427)

* feat(failover): add auto-failover master switch with proxy integration

- Add persistent auto_failover_enabled setting in database
- Add get/set_auto_failover_enabled commands
- Provider router respects master switch state
- Proxy shutdown automatically disables failover
- Enabling failover auto-starts proxy server
- Optimistic updates for failover queue toggle

* feat(proxy): persist proxy takeover state across app restarts

- Add proxy_takeover_{app_type} settings for per-app state tracking
- Restore proxy takeover state automatically on app startup
- Preserve state on normal exit, clear on manual stop
- Add stop_with_restore_keep_state method for graceful shutdown

* fix(proxy): set takeover state for all apps in start_with_takeover

src/components/proxy/ProxyToggle.tsx

@@ -49,10 +49,7 @@ export function ProxyToggle({ className, activeApp }: ProxyToggleProps) {
 
   return (
     <div
-      className={cn(
-        "p-1 rounded-xl transition-all",
-        className,
-      )}
+      className={cn("p-1 rounded-xl transition-all", className)}
       title={tooltipText}
     >
       <div className="flex items-center gap-2 px-2 h-8 rounded-md cursor-default">