ansible: delete the duplicated vars files, move globals to group_vars/all

Three files existed only as second copies of things group_vars/all already
auto-loads, and 34 playbooks named them in vars_files: - which outranks
group_vars, so the copies won. The day someone edited one and not the other,
those plays would silently keep the stale value. infra_vars.yml was already
drifting: group_vars/all/main.yml had grown age_backup_recipient and
backup_pull_public_key that it lacked.

  infra_vars.yml          - a strict subset of group_vars/all/main.yml
  infra_secrets.yml       - decrypts byte-identical to group_vars/all/vault.yml
  infra_secrets.yml.example - documented Uptime Kuma credentials as the reason
                              the file exists, which stopped being true

Deleted, along with 62 vars_files entries across 34 playbooks (12 of which
named ../../group_vars/all/main.yml directly - same defect, a vars_files entry
duplicating an auto-loaded file at higher precedence than the file itself).

Checked before touching anything: infra_secrets.yml was listed LAST in 10 plays,
after services_config.yml, so removal would flip precedence if the two shared a
key. They share none, and neither does services_config.yml with
group_vars/all/main.yml, so the removal is provably inert.

services_config.yml was the last one standing. It held four unrelated things:

  caddy_sites_dir            - an identical copy of roles/caddy_site/defaults/.
                               Deleted; the role default is now the only one.
  *.tailscale_hostname (x3)  - a THIRD copy of each box's identity, which
                               inventory.ini already holds as ansible_host.
                               Deleted. Edge plays now read
                               hostvars['<host>'].ansible_host - verified an
                               edge play resolves that with nothing loaded and
                               the other host in no play. Three copies of one
                               name is how bitcoin_rpc_host ended up labelled
                               "knots_box" while pointing at fulcrum-box.
  subdomains, ntfy topic,    - genuinely global: their readers span managed,
  headscale namespace          monitoring, vpn_control and edge, so no single
                               group covers them. Moved to group_vars/all/main.yml
                               where they auto-load. The ntfy_topic and
                               headscale_namespace indirection through
                               service_settings collapses to the global name.
  the four cross-host ports  - the only entries with a real justification.
                               Left in place; they move in the next commit.

Also dead, all Uptime Kuma residue or duplication:
  phoenixd_monitor_name, forgejo_runner healthcheck_timeout_seconds/retries,
  fulcrum_tailscale_hostname, and bitcoin_knots_version - the last being a
  v-prefixed copy of bitcoin_knots_version_short that nothing read, two
  hand-maintained copies of one version string.

Corrected a false comment: services_config.yml claimed the uptime_kuma subdomain
"no longer resolves to anything". It resolves to 164.92.239.72 and answers HTTP
302, and 11 playbooks still template it. Same wrong premise as PLAN_3.

Verification: all 37 playbooks' --list-tasks output is byte-identical before and
after. A probe resolving all 22 values services_config.yml used to supply returns
21 identical and one intended deletion (caddy_sites_dir, now role-only - confirmed
the role still resolves it: "Ensure Caddy sites-enabled directory exists" comes
back ok against the real path). memos check-diff identical before and after.
Syntax passes on every playbook.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ansible/infra/nodito/34_nut_ups_setup_playbook.yml

@@ -1,8 +1,6 @@
 - name: Setup NUT (Network UPS Tools) for CyberPower UPS
   hosts: hypervisor
   become: true
-  vars_files:
-    - ../../infra_vars.yml
 
   tasks:
     # ------------------------------------------------------------------
@@ -253,8 +251,6 @@
 - name: Setup UPS Heartbeat Monitoring
   hosts: hypervisor
   become: true
-  vars_files:
-    - ../../infra_vars.yml
 
   vars:
     ups_heartbeat_interval_seconds: 60