Migrate to rootful container architecture with infrastructure fact pattern

Major architectural change from rootless user services to system-level (rootful)
containers to enable group-based Unix socket access for containerized applications.

Infrastructure Changes:
- PostgreSQL: Export postgres-clients group GID as Ansible fact
- Valkey: Export valkey-clients group GID as Ansible fact
- Valkey: Add socket-fix service to maintain correct socket group ownership
- Both: Set socket directories to 770 with client group ownership

Authentik Role Refactoring:
- Remove rootless container configuration (subuid/subgid, lingering, user systemd)
- Deploy Quadlet files to /etc/containers/systemd/ (system-level)
- Use dynamic GID facts in container PodmanArgs (--group-add)
- Simplify user creation to system user with infrastructure group membership
- Update handlers for system scope service management
- Remove unnecessary container security options (no user namespace isolation)

Container Template Changes:
- Pod: Remove --userns args, change WantedBy to multi-user.target
- Containers: Replace Annotation with PodmanArgs using dynamic GIDs
- Remove /dev/shm mounts and SecurityLabelDisable (not needed for rootful)
- Change WantedBy to multi-user.target for system services

Documentation Updates:
- Add ADR-005: Rootful Containers with Infrastructure Fact Pattern
- Update ADR-003: Podman + systemd for system-level deployment
- Update authentik-deployment-guide.md for system scope commands
- Update service-integration-guide.md with rootful pattern examples
- Document discarded rootless approach and rationale

Why Rootful Succeeds:
- Direct UID/GID mapping preserves supplementary groups
- Container process groups match host socket group ownership
- No user namespace remapping breaking permissions

Why Rootless Failed (Discarded):
- User namespace UID/GID remapping broke group-based socket access
- Supplementary groups remapped into subgid range didn't match socket ownership
- Even with --userns=host and keep_original_groups, permissions failed

Pattern Established:
- Infrastructure roles create client groups and export GID facts
- Application roles validate facts and consume in container templates
- Rootful containers run as dedicated users with --group-add for socket access
- System-level deployment provides standard systemd service management

Deployment Validated:
- Services in /system.slice/ ✓
- Process groups: 961 (valkey-clients), 962 (postgres-clients), 966 (authentik) ✓
- Socket permissions: 770 with client groups ✓
- HTTP endpoint responding ✓

roles/authentik/tasks/database.yml

@@ -1,19 +1,12 @@
 ---
 # Database setup for Authentik - Self-contained socket permissions
 
-- name: Add authentik user to postgres group for socket access
+- name: Add authentik user to PostgreSQL client group for socket access
   user:
     name: "{{ authentik_user }}"
-    groups: postgres
+    groups: "{{ postgresql_client_group }}"
     append: true
 
-- name: Ensure authentik can access PostgreSQL socket directory
-  file:
-    path: "{{ postgresql_unix_socket_directories }}"
-    mode: '0770'
-    group: postgres
-  become: true
-
 - name: Test PostgreSQL socket connectivity
   postgresql_ping:
     login_unix_socket: "{{ postgresql_unix_socket_directories }}"