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

server/api/auth/me.get.ts

@@ -0,0 +1,61 @@
+// server/api/auth/me.get.ts
+
+/**
+ * GET /api/auth/me
+ *
+ * Get current authenticated user
+ *
+ * Response:
+ * {
+ *   "id": "uuid",
+ *   "experimentaId": "cidaas-sub",
+ *   "email": "user@example.com",
+ *   "firstName": "Max",
+ *   "lastName": "Mustermann",
+ *   ...
+ * }
+ *
+ * Returns 401 if not authenticated
+ */
+
+import { eq } from 'drizzle-orm'
+import { users } from '../../database/schema'
+
+export default defineEventHandler(async (event) => {
+  // 1. Require authentication (throws 401 if not logged in)
+  const { user: sessionUser } = await requireUserSession(event)
+
+  // 2. Fetch fresh user data from database
+  const db = useDatabase()
+  const user = await db.query.users.findFirst({
+    where: eq(users.id, sessionUser.id),
+  })
+
+  if (!user) {
+    throw createError({
+      statusCode: 404,
+      statusMessage: 'User not found',
+    })
+  }
+
+  // 3. Return user profile (exclude sensitive fields if any)
+  return {
+    id: user.id,
+    experimentaId: user.experimentaId,
+    email: user.email,
+    firstName: user.firstName,
+    lastName: user.lastName,
+    phone: user.phone,
+
+    // Billing address
+    salutation: user.salutation,
+    dateOfBirth: user.dateOfBirth,
+    street: user.street,
+    postCode: user.postCode,
+    city: user.city,
+    countryCode: user.countryCode,
+
+    createdAt: user.createdAt,
+    updatedAt: user.updatedAt,
+  }
+})