add SSH server configuration playbook and templates

playbooks/deploy_sshd_config.yml

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+---
+- name: Deploy complete SSH server configuration
+  hosts: all
+  become: true
+  gather_facts: false
+
+  tasks:
+    - name: Deploy base /etc/ssh/sshd_config file
+      template:
+        src: templates/sshd/sshd_config.j2
+        dest: /etc/ssh/sshd_config
+        owner: root
+        group: root
+        mode: "0644"
+      notify: Reload SSH
+
+    - name: Deploy hardened global ssh config include
+      template:
+        src: templates/sshd/00-global.conf.j2
+        dest: /etc/ssh/sshd_config.d/00-global.conf
+        owner: root
+        group: root
+        mode: "0644"
+      notify: Reload SSH
+
+    - name: Deploy LAN password bypass config include
+      template:
+        src: templates/sshd/99-lan-bypass.conf.j2
+        dest: /etc/ssh/sshd_config.d/99-lan-bypass.conf
+        owner: root
+        group: root
+        mode: "0644"
+      notify: Reload SSH
+
+    - name: Validate sshd configuration syntax
+      command: sshd -t
+      changed_when: false
+
+  handlers:
+    - name: Reload SSH
+      service:
+        name: ssh
+        state: reloaded

playbooks/templates/sshd/00-global.conf.j2

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+Port 22
+AddressFamily inet
+PermitRootLogin no
+
+PasswordAuthentication no
+KbdInteractiveAuthentication no
+ChallengeResponseAuthentication no
+PermitEmptyPasswords no
+
+UsePAM yes
+AllowGroups {{ ssh_access_group | default('sshusers') }}
+
+PubkeyAuthentication yes
+AuthorizedKeysFile .ssh/authorized_keys
+
+X11Forwarding no
+PrintMotd no
+PrintLastLog yes
+
+LoginGraceTime 30s
+MaxAuthTries 3
+MaxSessions 2
+
+AcceptEnv LANG LC_*
+Subsystem sftp /usr/lib/openssh/sftp-server

playbooks/templates/sshd/99-lan-bypass.conf.j2

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+Match Address 10.0.0.0/8
+    PasswordAuthentication yes

playbooks/templates/sshd/sshd_config.j2

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+# Base sshd_config — managed by Ansible
+# Delegates all settings to config fragments
+
+Include /etc/ssh/sshd_config.d/*.conf