Add sanoid Ansible role for ZFS snapshots and replication

Replaces manually deployed config files with a fully idempotent role:
installs sanoid, templates sanoid.conf and syncoid service/timer from
variables, enables both systemd timers. Removes static proxmox/sanoid.*
files. README rebuild section updated accordingly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ansible/roles/sanoid/templates/sanoid.conf.j2

@@ -0,0 +1,19 @@
+{% for entry in sanoid_datasets %}
+[{{ entry.dataset }}]
+    use_template = {{ entry.template }}
+{% if entry.recursive %}
+    recursive = yes
+{% endif %}
+
+{% endfor %}
+{% for name, t in sanoid_templates.items() %}
+[template_{{ name }}]
+    daily = {{ t.daily }}
+    weekly = {{ t.weekly }}
+    monthly = {{ t.monthly }}
+    hourly = {{ t.hourly }}
+    frequently = {{ t.frequently }}
+    autosnap = {{ 'yes' if t.autosnap else 'no' }}
+    autoprune = {{ 'yes' if t.autoprune else 'no' }}
+
+{% endfor %}