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/postgresql/tasks/main.yml

@@ -11,6 +11,19 @@
     name: python-psycopg2
     state: present
 
+- name: Create PostgreSQL client access group
+  group:
+    name: "{{ postgresql_client_group }}"
+    system: true
+  when: postgresql_client_group_create
+
+- name: Ensure postgres user is in client group
+  user:
+    name: postgres
+    groups: "{{ postgresql_client_group }}"
+    append: true
+  when: postgresql_client_group_create
+
 - name: Check if PostgreSQL data directory exists and is initialized
   stat:
     path: "/var/lib/postgres/data/PG_VERSION"
@@ -72,10 +85,21 @@
     path: "{{ postgresql_unix_socket_directories }}"
     state: directory
     owner: postgres
-    group: postgres
+    group: "{{ postgresql_client_group }}"
     mode: '0770'
   when: postgresql_unix_socket_enabled
 
+- name: Get PostgreSQL client group GID for containerized applications
+  shell: "getent group {{ postgresql_client_group }} | cut -d: -f3"
+  register: postgresql_client_group_lookup
+  changed_when: false
+  when: postgresql_client_group_create
+
+- name: Set PostgreSQL client group GID as fact
+  set_fact:
+    postgresql_client_group_gid: "{{ postgresql_client_group_lookup.stdout }}"
+  when: postgresql_client_group_create and postgresql_client_group_lookup.stdout is defined
+
 - name: Enable and start PostgreSQL service
   systemd:
     name: postgresql