feat: User Logout support

[guenhter]

Add user logout support

[Copilot]

Pull request overview

Adds user logout support end-to-end (backend CSRF + logout endpoints, frontend sidebar UI), and updates session/userinfo handling to support showing the logged-in user in the sidebar.

Changes:

• Add backend CSRF (GET /api/auth/csrf) and CSRF-protected logout (POST /api/auth/logout) flow.
• Replace the old session probe with GET /api/auth/userinfo returning user_id, name, and additional, and update frontend session service to be stateless and return session state directly.
• Add sidebar footer area with Logout + User Avatar items, plus updated unit/e2e tests and docs/changelogs.

Reviewed changes

Copilot reviewed 34 out of 34 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
justfile	Adds root recipes to run install/format across subprojects.
frontend/omni/src/modules/user-avatar/locales/de.json	Adds German label for user avatar.
frontend/omni/src/modules/user-avatar/UserAvatarItem.svelte	New sidebar item showing user initials/name from session state.
frontend/omni/src/modules/session-service/sessionServiceImpl.test.ts	Updates tests for new getActiveSession() behavior and userInfo handling.
frontend/omni/src/modules/session-service/sessionServiceImpl.svelte.ts	Replaces cached session state with stateless getActiveSession() fetching /api/auth/userinfo.
frontend/omni/src/modules/session-service/index.svelte.ts	Introduces SessionState/UserInfo types and new SessionService API.
frontend/omni/src/modules/session-service/SessionGatedAppLayout.svelte	Switches gating logic to use getActiveSession() return value.
frontend/omni/src/modules/main-app-sidebar-based/lib/styles.ts	Centralizes sidebar menu button class string.
frontend/omni/src/modules/main-app-sidebar-based/lib/SidebarMenuNavigationItem.svelte	Removes old navigation item component (inlined elsewhere).
frontend/omni/src/modules/main-app-sidebar-based/SidebarLayout.svelte	Adds sidebar footer slot/snippet support.
frontend/omni/src/modules/main-app-sidebar-based/MainApp.svelte	Renders top + bottom sidebar items via new footer snippet.
frontend/omni/src/modules/llm-provider-management/providersNavigationItem.svelte	Inlines sidebar menu item rendering using shared styles.
frontend/omni/src/modules/fetch-service/sessionFetchService.svelte.ts	Updates 401 handling to use getActiveSession().
frontend/omni/src/modules/fetch-service/fetchService.test.ts	Updates mocks/assertions for getActiveSession() API.
frontend/omni/src/modules/chat/chatNavigationItem.svelte	Inlines sidebar menu item rendering using shared styles.
frontend/omni/src/modules/authentication/locales/de.json	Adds German label for logout.
frontend/omni/src/modules/authentication/LogoutItem.svelte	Adds logout sidebar item calling /api/auth/csrf then POST /api/auth/logout.
frontend/omni/public/modules_with_backend.json	Wires logout + avatar into sidebar bottom items; adds module entries.
frontend/omni/public/modules_browser_only.json	Adds (empty) sidebar bottom items wiring for browser-only config.
frontend/omni/docs/learnings/INSTRUCTION_UPDATES.md	Documents “frontend services must be stateless” guidance.
frontend/omni/CHANGELOG.md	Documents new sidebar avatar + logout button additions.
e2e_tests/tests_omni_full/src/pages.ts	Adds sidebar page-object logout helper.
e2e_tests/tests_omni_full/src/login.spec.ts	Updates session checks to /api/auth/userinfo and enables logout e2e test.
backend/omni/src/modai/modules/session/oidc_session.py	Removes user_store/JIT provisioning; session validation now includes name.
backend/omni/src/modai/modules/session/module.py	Changes session endpoint path to /api/auth/userinfo; adds name to Session model.
backend/omni/src/modai/modules/session/dev_mock_session.py	Updates mock session to include name field.
backend/omni/src/modai/modules/session/tests/test_oidc_session.py	Updates tests for new endpoint and name field; removes user_store/JIT tests.
backend/omni/src/modai/modules/session/README.md	Updates docs for /api/auth/userinfo and Session model changes.
backend/omni/src/modai/modules/chat/tests/test_web_chat_router.py	Updates Session construction for new name field.
backend/omni/src/modai/modules/authentication/oidc_auth_module.py	Adds CSRF endpoint and CSRF validation for logout.
backend/omni/src/modai/modules/authentication/tests/test_oidc_auth_module.py	Adds CSRF/logout tests and updates logout tests to include CSRF header.
backend/omni/docs/architecture/auth.md	Updates auth/session docs for new endpoints, CSRF, and session payload shape.
backend/omni/CHANGELOG.md	Documents new CSRF/logout endpoints and userinfo payload/endpoint consolidation.
CONTRIBUTION.md	Fixes spelling/grammar and clarifies AI-assisted workflow expectations.

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