Implement authentication phase with Cidaas OAuth2 integration

- Add authentication middleware to protect routes
- Create API endpoints for login, logout, registration, and user info
- Develop UI components for login and registration forms
- Integrate VeeValidate for form validation
- Update environment configuration for Cidaas settings
- Add i18n support for English and German languages
- Enhance Tailwind CSS for improved styling of auth components
- Document authentication flow and testing procedures

app/components/ui/alert/Alert.vue

@@ -0,0 +1,21 @@
+<script setup lang="ts">
+import type { HTMLAttributes } from 'vue'
+import type { AlertVariants } from '.'
+import { cn } from '~/lib/utils'
+import { alertVariants } from '.'
+
+interface Props {
+  variant?: AlertVariants['variant']
+  class?: HTMLAttributes['class']
+}
+
+const props = withDefaults(defineProps<Props>(), {
+  variant: 'default',
+})
+</script>
+
+<template>
+  <div :class="cn(alertVariants({ variant }), props.class)" role="alert">
+    <slot />
+  </div>
+</template>