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/DropdownMenuLabel.vue

@@ -0,0 +1,22 @@
+<script setup lang="ts">
+import type { DropdownMenuLabelProps } from "reka-ui"
+import type { HTMLAttributes } from "vue"
+import { reactiveOmit } from "@vueuse/core"
+import { DropdownMenuLabel, useForwardProps } from "reka-ui"
+import { cn } from '~/lib/utils'
+
+const props = defineProps<DropdownMenuLabelProps & { class?: HTMLAttributes["class"], inset?: boolean }>()
+
+const delegatedProps = reactiveOmit(props, "class")
+
+const forwardedProps = useForwardProps(delegatedProps)
+</script>
+
+<template>
+  <DropdownMenuLabel
+    v-bind="forwardedProps"
+    :class="cn('px-2 py-1.5 text-sm font-semibold', inset && 'pl-8', props.class)"
+  >
+    <slot />
+  </DropdownMenuLabel>
+</template>