fix(e2e): get all E2E tests passing and fix AlertDialog crash on delete

- Fix rate limiter to allow 100 attempts in dev mode so E2E tests are
  not blocked by failed-login attempts during test development
- Simplify logout button selector to use Lucide icon class (lucide-log-out)
  instead of the fragile Tooltip-content locator chain that broke on navigation
- Rewrite stacks E2E spec: use waitForFunction to wait for sidebar to load,
  delete leftover stacks via browser-context fetch before creating, and use
  page.reload() to get a clean sidebar state
- Fix AlertDialogContent: remove asChild+motion.div pattern that triggered a
  React.Children.only crash — Radix AlertDialog.Content injects a second
  DescriptionWarning child internally, breaking Slot when asChild=true; replace
  with CSS keyframe animations (data-[state=open]:animate-in)
- Fix final assertion in delete test to use exact text + listbox scope to avoid
  false positives from similarly-named stacks like e2e-test-stack-*
- All 6 E2E tests pass (4 auth + 2 stacks); node tests skip gracefully

frontend/src/components/ui/alert-dialog.tsx

@@ -30,18 +30,16 @@ const AlertDialogContent = React.forwardRef<
 >(({ className, children, ...props }, ref) => (
   <AlertDialogPortal>
     <AlertDialogOverlay />
-    <AlertDialogPrimitive.Content ref={ref} asChild {...props}>
-      <motion.div
-        className={cn(
-          'fixed left-[50%] top-[50%] z-50 grid w-full max-w-lg translate-x-[-50%] translate-y-[-50%] gap-4 border bg-background p-6 shadow-lg sm:rounded-lg',
-          className
-        )}
-        initial={{ opacity: 0, scale: 0.92, y: -12 }}
-        animate={{ opacity: 1, scale: 1, y: 0 }}
-        transition={{ type: 'spring', stiffness: 380, damping: 32 }}
-      >
-        {children}
-      </motion.div>
+    <AlertDialogPrimitive.Content
+      ref={ref}
+      className={cn(
+        'fixed left-[50%] top-[50%] z-50 grid w-full max-w-lg translate-x-[-50%] translate-y-[-50%] gap-4 border bg-background p-6 shadow-lg sm:rounded-lg',
+        'data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95',
+        className
+      )}
+      {...props}
+    >
+      {children}
     </AlertDialogPrimitive.Content>
   </AlertDialogPortal>
 ));