docs(claude): add auth/ package row, drop auth-controllers from user/

PR #523 moved login/logout into a new auth/ package (AuthSessionController,
AuthService, LoginRequest) — register the row in both CLAUDE.md trees
alphabetically and strip the stale "auth controllers" line from the user/
description so the next LLM reading either file finds the right home.
Addresses PR #612 / Markus M1.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/CLAUDE.md

@@ -24,6 +24,7 @@ Spring Boot 4.0 monolith serving the Familienarchiv REST API. Handles document m
 ```
 src/main/java/org/raddatz/familienarchiv/
 ├── audit/               # Audit logging (AuditService, AuditLogQueryService)
+├── auth/                # AuthService, AuthSessionController, LoginRequest (Spring Session JDBC — ADR-020)
 ├── config/              # Infrastructure config (MinioConfig, AsyncConfig, WebConfig)
 ├── dashboard/           # Dashboard analytics + StatsController/StatsService
 ├── document/            # Document domain — entities, controller, service, repository, DTOs
@@ -40,7 +41,7 @@ src/main/java/org/raddatz/familienarchiv/
 │   └── relationship/    # PersonRelationship sub-domain
 ├── security/            # SecurityConfig, Permission, @RequirePermission, PermissionAspect
 ├── tag/                 # Tag domain — Tag, TagService, TagController
-└── user/                # User domain — AppUser, UserGroup, UserService, auth controllers
+└── user/                # User domain — AppUser, UserGroup, UserService
 ```
 
 For per-domain ownership and public surface, see each domain's `README.md`.