Implement client-side route protection with role-based access control. The auth
store now extracts the role claim from JWT tokens and exposes isAdmin. Router
guards enforce three levels of access: guestOnly (redirect authenticated users),
requiresAuth (redirect unauthenticated to login with redirect param), and
requiresAdmin (redirect non-admin users to home).
Changes:
- utils/jwt.ts: JWT payload parser using base64url decode (new file)
- authStore: add role ref, isAdmin computed, extractRole from JWT payload
- router: add route metadata (requiresAuth, requiresAdmin, guestOnly) and
beforeEach guard with getActivePinia() safety for test environments
- OrdersPage.vue, AdminPage.vue: placeholder pages (new files)
- LoginPage.vue, RegisterPage.vue: use route.query.redirect after auth
- Router.spec.ts: 14 tests covering all guard scenarios
- authStore.spec.ts: tests for role extraction, isAdmin, role persistence
- LoginPage.spec.ts: test for redirect query param after login
- auth-guards.spec.ts: 7 Playwright E2E tests for guard behavior
- login.spec.ts: fix seed user credentials (test@bilhalsning.se)
