Fix playbook bugs from review, add Telegram alerts to health and service checks

Review fixes:
- Availability plays: "ping_result is succeeded" is true for unreachable
  hosts, so offline hosts were added to reachable_hosts and failed the
  next play. Test reachability explicitly (7 playbooks).
- bootstrap_lxc: vim-enhanced and mtr-tiny package names, enable CRB next
  to EPEL, add the root key without replacing authorized_keys, validate
  sshd_config edits and restart sshd only on change.
- backup_docker: the command module does not expand $(...); fix rsync
  filter order and add --exclude=*; restart only the containers that were
  stopped, even when rsync fails; read the storage address from the
  inventory; keep semaphore and semaphore-db running.
- new_lxc: community.general.proxmox no longer exists, use
  community.proxmox; node is mini-pc; valid hostname; password or token
  auth; let the module pick the VMID; longer timeout.
- proxmox-backup: surface the vzdump exit code, let vzdump prune with
  keep-last, drop the rename/prune steps that globbed *.zstd.
- time-region: chrony regex no longer comments out its own server line;
  /etc/localtime as a symlink; reuse facts across plays.
- update_pihole_blocklists: FQCN, become: true, changed_when.
- ansible.cfg gathering = smart; update_system only pings ubuntu/rocky.

Telegram alerts:
- health_check: filesystems above disk_warn_pct (default 80), excluding
  efivarfs, and offline hosts.
- service_check: services not running.
- One message per run from localhost, credentials from Semaphore
  (TELEGRAM_BOT_TOKEN / TELEGRAM_CHAT_ID), no_log on the send task,
  prints the alert text when Telegram is not configured.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XEizHawueRXUcxQELRZ8kq

playbooks/time-region.yml

@@ -1,30 +1,46 @@
 ---
-- name: Configure timezone on all hosts
+# Sets the timezone on every Ubuntu/Rocky guest. LXC containers share the
+# host's clock, so NTP is disabled inside them; VMs sync against ntp_server.
+#
+# Extra vars (optional):
+#   timezone_region - default America/New_York
+#   ntp_server      - default time.google.com
+
+- name: Configure timezone
   hosts: ubuntu:rocky
   become: true
-  gather_facts: true
 
   vars:
-    timezone_region: "America/New_York"
+    timezone_region: America/New_York
 
   tasks:
-    - name: Copy timezone file
-      ansible.builtin.copy:
+    - name: Link /etc/localtime to the zoneinfo file
+      ansible.builtin.file:
         src: "/usr/share/zoneinfo/{{ timezone_region }}"
         dest: /etc/localtime
-        remote_src: true
+        state: link
+        force: true
 
     - name: Write /etc/timezone
       ansible.builtin.copy:
         dest: /etc/timezone
         content: "{{ timezone_region }}\n"
+        owner: root
+        group: root
+        mode: '0644'
 
-- name: Disable NTP on Ubuntu LXC containers
+# The plays below reuse the facts gathered above instead of collecting them again.
+
+- name: NTP on Ubuntu
   hosts: ubuntu
   become: true
+  gather_facts: false
+
+  vars:
+    ntp_server: time.google.com
 
   tasks:
-    - name: Stop and mask timesyncd on LXC
+    - name: Stop and mask timesyncd in LXC containers
       ansible.builtin.systemd:
         name: systemd-timesyncd
         state: stopped
@@ -32,33 +48,11 @@
         masked: true
       when: ansible_virtualization_type == "lxc"
 
-- name: Disable NTP on Rocky Linux LXC containers
-  hosts: rocky
-  become: true
-
-  tasks:
-    - name: Stop and mask chronyd on LXC
-      ansible.builtin.systemd:
-        name: chronyd
-        state: stopped
-        enabled: false
-        masked: true
-      when: ansible_virtualization_type == "lxc"
-
-- name: Configure NTP on Ubuntu VMs
-  hosts: ubuntu
-  become: true
-
-  vars:
-    ntp_server: "time.google.com"
-
-  tasks:
-    - name: Configure timesyncd
+    - name: Point timesyncd at ntp_server on VMs
       ansible.builtin.lineinfile:
         path: /etc/systemd/timesyncd.conf
         regexp: '^#?NTP='
         line: "NTP={{ ntp_server }}"
-        state: present
       when: ansible_virtualization_type != "lxc"
       notify: Restart timesyncd
 
@@ -69,27 +63,38 @@
         state: restarted
         enabled: true
 
-- name: Configure NTP on Rocky Linux VMs
+- name: NTP on Rocky Linux
   hosts: rocky
   become: true
+  gather_facts: false
 
   vars:
-    ntp_server: "time.google.com"
+    ntp_server: time.google.com
 
   tasks:
-    - name: Disable default chrony pools
+    - name: Stop and mask chronyd in LXC containers
+      ansible.builtin.systemd:
+        name: chronyd
+        state: stopped
+        enabled: false
+        masked: true
+      when: ansible_virtualization_type == "lxc"
+
+    # The lookahead keeps the server line added below from being commented
+    # out again on the next run.
+    - name: Disable the default chrony pools on VMs
       ansible.builtin.replace:
         path: /etc/chrony.conf
-        regexp: '^(pool|server) .*'
-        replace: '# \1 removed by Ansible'
+        regexp: '^(pool|server)\s+(?!{{ ntp_server | regex_escape }}(\s|$)).*'
+        replace: '# \g<0>  (disabled by Ansible)'
       when: ansible_virtualization_type != "lxc"
+      notify: Restart chronyd
 
-    - name: Configure chrony NTP server
+    - name: Point chrony at ntp_server on VMs
       ansible.builtin.lineinfile:
         path: /etc/chrony.conf
+        regexp: '^server\s+{{ ntp_server | regex_escape }}(\s|$)'
         line: "server {{ ntp_server }} iburst"
-        insertafter: EOF
-        state: present
       when: ansible_virtualization_type != "lxc"
       notify: Restart chronyd
 
@@ -103,6 +108,7 @@
 - name: Verify time configuration
   hosts: ubuntu:rocky
   become: true
+  gather_facts: false
 
   tasks:
     - name: Check current system time