ansible: move the cross-host ports to host_vars, delete services_config.yml

The four ports were the only entries in services_config.yml with a real
justification: each is read twice, by the role that deploys the service on its
own box AND by a socket-proxy or Caddy play that runs on the EDGE host and
publishes it. A role default is invisible to that second play.

But the shape was wrong in two ways. The file had to be named in vars_files: by
30 plays - opt-in configuration that someone will eventually forget - and five
role defaults silently interpolated service_settings.*, so bitcoin_knots,
fulcrum, datum_gateway and mempool were not self-contained: using any of them
without that one vars_file entry broke it.

Each port now lives in host_vars/<owning box>/main.yml:

  host_vars/knots_box_local/main.yml    bitcoin_p2p_port, datum_gateway_api_port,
                                        datum_gateway_stratum_port
  host_vars/fulcrum_box_local/main.yml  fulcrum_ssl_port
  host_vars/mempool_box_local/main.yml  mempool_frontend_port

host_vars auto-loads and outranks role defaults, so the owning role picks the
value up with no vars_files at all, and the edge play reads the same single
definition as hostvars['<host>'].<name>. The role defaults keep the protocol
standard (8333, 50002, ...) so each role still works standalone, with the live
deployment's value in host_vars winning.

Also fixed a fourth copy of an inventory identity: the mempool Caddy play had
"mempool-box:{{ ... }}" hardcoded in the upstream. It now derives the host from
hostvars['mempool_box_local'].ansible_host, so inventory is the only place any
box's name is written down.

services_config.yml is deleted, with 25 more vars_files entries across 19
playbooks. Between this and the previous commit, 87 vars_files entries are gone
and every variable in the repo now comes from group_vars/all, host_vars,
inventory, a role default, or that service's own *_vars.yml.

Verification: an edge-host probe resolves all eight ports and hostnames to
byte-identical values to the ones services_config.yml used to supply. Each
owning host resolves its own port through host_vars. All 37 playbooks'
--list-tasks output is unchanged. The four edge plays that consume these values
all check-diff changed=0 - the socket-proxy and Caddy units on vipy are
byte-identical, which is the direct proof the rewiring landed on the same
values. fulcrum and datum-gateway check-diff exactly as before (ok=28/changed=1
and ok=15/changed=1, both the known timer re-arm).

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

ansible/services/datum-gateway/deploy_datum_gateway_playbook.yml

@@ -10,8 +10,6 @@
 - name: Deploy DATUM Gateway on the bitcoin host
   hosts: bitcoin
   become: yes
-  vars_files:
-    - ../../services_config.yml
   vars:
     # Preserves the push URL this check reports to. The role knows nothing about
     # Uptime Kuma — this is just "a URL that accepts a ping".
@@ -22,8 +20,6 @@
 - name: Configure Caddy reverse proxy for the DATUM Gateway dashboard on the edge host
   hosts: edge
   become: yes
-  vars_files:
-    - ../../services_config.yml
   tasks:
     - name: Publish the DATUM Gateway dashboard through Caddy
       ansible.builtin.include_role:
@@ -31,7 +27,7 @@
       vars:
         caddy_site_name: datum-gateway
         caddy_site_domain: "{{ subdomains.datum_gateway }}.{{ root_domain }}"
-        caddy_site_upstream: "{{ hostvars['knots_box_local'].ansible_host }}:{{ service_settings.datum_gateway.api_port }}"
+        caddy_site_upstream: "{{ hostvars['knots_box_local'].ansible_host }}:{{ hostvars['knots_box_local'].datum_gateway_api_port }}"
         caddy_site_resolvers: "100.100.100.100"
         caddy_site_basic_auth:
           - user: "{{ datum_dashboard_username }}"
@@ -47,8 +43,6 @@
 - name: Setup public Stratum port forwarding on the edge host
   hosts: edge
   become: yes
-  vars_files:
-    - ../../services_config.yml
   tasks:
     - name: Expose the DATUM Stratum port through a socket proxy
       ansible.builtin.include_role:
@@ -56,7 +50,7 @@
       vars:
         socket_proxy_name: datum-stratum
         socket_proxy_description: "DATUM Stratum"
-        socket_proxy_listen_port: "{{ service_settings.datum_gateway.stratum_port }}"
+        socket_proxy_listen_port: "{{ hostvars['knots_box_local'].datum_gateway_stratum_port }}"
         socket_proxy_upstream_host: "{{ hostvars['knots_box_local'].ansible_host }}"
         # Matches the UFW comment already on the edge host; the derived default
         # would say "DATUM Stratum" and rewrite the rule.