Phase 1 auth security hotfixes: cookie-based session, bearer checks, router guard sync ...

- Remove access_token from OAuth callback URL (token leak fix)
- Add sanitizeReturnTo() to prevent open redirect on login/callback
- Add Bearer token expiration check in resolve_user_by_bearer()
- Add user status check in load_user_by_id() (block inactive/banned)
- Cache authStore.init() promise to prevent race condition
- Await auth init in router beforeEach guard
- Remove URL token parsing from main.js and LoginPage
- Remove hasTokenInUrl workaround from client.js 401 handler

Fix OAuth callback: extract access_token in main.js before auth init, prevent 401 redirect loop in client.js

Phase 4: Vue client auth store, Bearer token injection, router guards, login page ...

Server:
- AuthControllerTrait now supports both session and Bearer token auth
  (resolves user from Authorization: Bearer header via shserv_sessions)

Vue client:
- Add api/auth.js module for access token management
- Inject Authorization: Bearer header in http.js
- Handle 401 in client.js: clear token + redirect to /auth/login
- New Pinia auth store (stores/auth.js): init, refreshToken, logout, hasPermission
- New usePermission composable
- Router guards: redirect unauthenticated to /login, permission-based route blocking
- New LoginPage.vue with gnexus-auth login button
- AppShell: conditional nav items by permission, user bar with logout
- main.js: initialize auth before mounting app
- MSW mocks: /auth/me, /auth/logout, /auth/refresh
- Fix AppShell.spec.js for Pinia + router setup

All 167 tests pass.

Phase 6: Rename webclient-vue to webclient, match legacy dist structure