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/avatar/index.ts

@@ -0,0 +1,25 @@
+import type { VariantProps } from "class-variance-authority"
+import { cva } from "class-variance-authority"
+
+export { default as Avatar } from "./Avatar.vue"
+export { default as AvatarFallback } from "./AvatarFallback.vue"
+export { default as AvatarImage } from "./AvatarImage.vue"
+
+export const avatarVariant = cva(
+  "inline-flex items-center justify-center font-normal text-foreground select-none shrink-0 bg-secondary overflow-hidden",
+  {
+    variants: {
+      size: {
+        sm: "h-10 w-10 text-xs",
+        base: "h-16 w-16 text-2xl",
+        lg: "h-32 w-32 text-5xl",
+      },
+      shape: {
+        circle: "rounded-full",
+        square: "rounded-md",
+      },
+    },
+  },
+)
+
+export type AvatarVariants = VariantProps<typeof avatarVariant>