Implement Password Grant Flow for Authentication and Enhance User Experience

- Introduced Password Grant Flow for user authentication, allowing direct login with email and password.
- Updated `useAuth` composable to manage login and logout processes, including Single Sign-Out from Cidaas.
- Enhanced user interface with a new `UserMenu` component displaying user information and logout functionality.
- Updated homepage to show personalized greetings for logged-in users and a login prompt for guests.
- Added logout confirmation page with a countdown redirect to the homepage.
- Documented the implementation details and future enhancements for OAuth2 flows in CLAUDE.md and other relevant documentation.
- Added test credentials and guidelines for automated testing in the new TESTING.md file.

app/components/ui/dropdown-menu/DropdownMenuCheckboxItem.vue

@@ -0,0 +1,37 @@
+<script setup lang="ts">
+import type { DropdownMenuCheckboxItemEmits, DropdownMenuCheckboxItemProps } from "reka-ui"
+import type { HTMLAttributes } from "vue"
+import { reactiveOmit } from "@vueuse/core"
+import { Check } from "lucide-vue-next"
+import {
+  DropdownMenuCheckboxItem,
+
+  DropdownMenuItemIndicator,
+  useForwardPropsEmits,
+} from "reka-ui"
+import { cn } from '~/lib/utils'
+
+const props = defineProps<DropdownMenuCheckboxItemProps & { class?: HTMLAttributes["class"] }>()
+const emits = defineEmits<DropdownMenuCheckboxItemEmits>()
+
+const delegatedProps = reactiveOmit(props, "class")
+
+const forwarded = useForwardPropsEmits(delegatedProps, emits)
+</script>
+
+<template>
+  <DropdownMenuCheckboxItem
+    v-bind="forwarded"
+    :class=" cn(
+      'relative flex cursor-default select-none items-center rounded-sm py-1.5 pl-8 pr-2 text-sm outline-none transition-colors focus:bg-accent focus:text-accent-foreground data-[disabled]:pointer-events-none data-[disabled]:opacity-50',
+      props.class,
+    )"
+  >
+    <span class="absolute left-2 flex h-3.5 w-3.5 items-center justify-center">
+      <DropdownMenuItemIndicator>
+        <Check class="w-4 h-4" />
+      </DropdownMenuItemIndicator>
+    </span>
+    <slot />
+  </DropdownMenuCheckboxItem>
+</template>