Implement Role Management Features and UI Enhancements

- Introduced a new composable `useActiveRole` for managing user roles, including fetching role status and switching roles with server validation.
- Updated `RoleSwitcher.vue` to utilize the new composable, enhancing role selection with improved error handling and UI feedback.
- Added new API endpoints for role management, including fetching user role status and switching active roles.
- Enhanced product visibility logic to filter based on the user's active role, ensuring a tailored experience.
- Updated database schema to support last active role tracking for users, improving session management.
- Refined UI components across the application to reflect role-based changes and improve user experience.

server/api/user/active-role.patch.ts

@@ -0,0 +1,64 @@
+/**
+ * PATCH /api/user/active-role
+ *
+ * Switch user's active role (used by RoleSwitcher component)
+ *
+ * Request body:
+ * {
+ *   "roleCode": "educator"
+ * }
+ *
+ * Response:
+ * {
+ *   "success": true,
+ *   "activeRoleCode": "educator"
+ * }
+ *
+ * Validates that user has the requested role before switching
+ * Updates both session (immediate) and database (preference)
+ */
+
+import { z } from 'zod'
+import { setUserActiveRole } from '../../utils/role-session'
+
+const switchRoleSchema = z.object({
+  roleCode: z.enum(['private', 'educator', 'company'], {
+    errorMap: () => ({ message: 'Ungültige Rolle' }),
+  }),
+})
+
+export default defineEventHandler(async (event) => {
+  // Require authentication
+  await requireUserSession(event)
+
+  // Validate request body
+  const body = await readBody(event)
+  const { roleCode } = switchRoleSchema.parse(body)
+
+  try {
+    // Set active role (validates + updates session + saves to DB)
+    await setUserActiveRole(event, roleCode)
+
+    return {
+      success: true,
+      activeRoleCode: roleCode,
+    }
+  } catch (error: any) {
+    // setUserActiveRole throws 403 if user doesn't have role
+    if (error.statusCode === 403) {
+      setResponseStatus(event, 403)
+      return {
+        success: false,
+        message: error.message || 'Du hast diese Rolle nicht',
+      }
+    }
+
+    // Other errors
+    console.error('Role switch error:', error)
+    setResponseStatus(event, 500)
+    return {
+      success: false,
+      message: 'Fehler beim Wechseln der Rolle',
+    }
+  }
+})