Add Synology DSM support (#5315)

Adds optional support for running the playbook on Synology DSM 7+, detected
automatically via /etc/synoinfo.conf so that non-Synology hosts are unaffected.

Includes DSM-native user/group management (synouser/synogroup), a requests
version constraint for Docker SDK compatibility, and a boot-fix service that
re-shares the volume mount and starts matrix services skipped by DSM's boot
ordering. The shared-mount volume path is configurable via
matrix_base_synology_volume_path, and the make-shared step only runs when the
volume is not already shared.

Co-authored-by: CKSit <sitchiuki@gmail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

roles/custom/matrix-base/tasks/main.yml

@@ -4,6 +4,7 @@
 # SPDX-FileCopyrightText: 2020 Marcel Partap
 # SPDX-FileCopyrightText: 2022 Marko Weltzer
 # SPDX-FileCopyrightText: 2022 Warren Bailey
+# SPDX-FileCopyrightText: 2026 Chiu Ki Sit
 #
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
@@ -15,6 +16,11 @@
   block:
     - ansible.builtin.include_tasks: "{{ role_path }}/tasks/validate_config.yml"
 
+- tags:
+    - always
+  block:
+    - ansible.builtin.include_tasks: "{{ role_path }}/tasks/detect_platform.yml"
+
 # This needs to always run, because it populates `matrix_user_uid` and `matrix_user_gid`,
 # which are required by many other roles.
 - tags:
@@ -24,6 +30,13 @@
   block:
     - ansible.builtin.include_tasks: "{{ role_path }}/tasks/setup_matrix_user.yml"
 
+- tags:
+    - setup-all
+    - install-all
+  block:
+    - ansible.builtin.include_tasks: "{{ role_path }}/tasks/setup_synology_prerequisites.yml"
+      when: matrix_base_host_is_synology
+
 - tags:
     - setup-all
     - install-all