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/DropdownMenuSubContent.vue

@@ -0,0 +1,27 @@
+<script setup lang="ts">
+import type { DropdownMenuSubContentEmits, DropdownMenuSubContentProps } from "reka-ui"
+import type { HTMLAttributes } from "vue"
+import { reactiveOmit } from "@vueuse/core"
+import {
+  DropdownMenuSubContent,
+
+  useForwardPropsEmits,
+} from "reka-ui"
+import { cn } from '~/lib/utils'
+
+const props = defineProps<DropdownMenuSubContentProps & { class?: HTMLAttributes["class"] }>()
+const emits = defineEmits<DropdownMenuSubContentEmits>()
+
+const delegatedProps = reactiveOmit(props, "class")
+
+const forwarded = useForwardPropsEmits(delegatedProps, emits)
+</script>
+
+<template>
+  <DropdownMenuSubContent
+    v-bind="forwarded"
+    :class="cn('z-50 min-w-32 overflow-hidden rounded-md border bg-popover p-1 text-popover-foreground shadow-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 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2', props.class)"
+  >
+    <slot />
+  </DropdownMenuSubContent>
+</template>