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/DropdownMenuSubTrigger.vue

@@ -0,0 +1,31 @@
+<script setup lang="ts">
+import type { DropdownMenuSubTriggerProps } from "reka-ui"
+import type { HTMLAttributes } from "vue"
+import { reactiveOmit } from "@vueuse/core"
+import { ChevronRight } from "lucide-vue-next"
+import {
+  DropdownMenuSubTrigger,
+
+  useForwardProps,
+} from "reka-ui"
+import { cn } from '~/lib/utils'
+
+const props = defineProps<DropdownMenuSubTriggerProps & { class?: HTMLAttributes["class"] }>()
+
+const delegatedProps = reactiveOmit(props, "class")
+
+const forwardedProps = useForwardProps(delegatedProps)
+</script>
+
+<template>
+  <DropdownMenuSubTrigger
+    v-bind="forwardedProps"
+    :class="cn(
+      'flex cursor-default select-none items-center rounded-sm px-2 py-1.5 text-sm outline-none focus:bg-accent data-[state=open]:bg-accent',
+      props.class,
+    )"
+  >
+    <slot />
+    <ChevronRight class="ml-auto h-4 w-4" />
+  </DropdownMenuSubTrigger>
+</template>