fulcrum: convert to a role, de-Uptime-Kuma the health check

685-line playbook becomes 33 lines plus a 426-line role
(install/service/healthcheck phases, six templates, one handler).
fulcrum_vars.yml is deleted; its content is the role's defaults.

Verified: fulcrum untouched - active since 2026-07-29 (no restart), 192G datadir,
height 966842, bitcoind and db_mem unchanged on disk. Second run changed=1 (the
arming run, changed_when: false aside). vipy changed=0.

THREE PRE-EXISTING LANDMINES the check-mode diff caught, any of which a faithful
extraction would have detonated:

- bitcoin_rpc_host was "192.168.1.140", commented "IP of knots_box_local". But
  .140 is fulcrum-box ITSELF; knots-box is .135. The DHCP leases had reshuffled -
  the fifth instance of this same disease in this estate. The live config had
  been hand-corrected to knots-box; running the playbook would have reverted it
  and pointed Fulcrum at itself. Now addressed by Tailscale name.

- The `Restart fulcrum` handler was guarded by uptime_kuma_enabled, so the three
  tasks that notify it (SSL cert, fulcrum.conf, systemd unit) could not restart
  anything. A config change applied to disk, reported success, and silently never
  took effect. That is worse than the other banner casualties: it makes the
  deployment itself lie. Ungated.

- db_mem was about to go 2048 -> 4448 (75% of 5931MB RAM), leaving ~1.4GB for the
  OS and Fulcrum's non-cache memory. The live value had been hand-tuned down.
  fulcrum_db_mem_mb_override pins it. Note set_fact outranks role defaults, so
  the calculation itself has to honour the override.

MY OWN ERROR, third instance: retyping `copy:` as `template:` lost `owner:` on
the banner and on fulcrum.conf. Rather than keep catching these by eye, every
managed path's owner/group/mode is now compared against `git show HEAD:`
mechanically - 12/12 match.

The health check timer had not fired since 2026-02-17 while reporting `active`
and `enabled`. It is OnBootSec + OnUnitActiveSec with no OnCalendar: OnBootSec
elapses once, and OnUnitActiveSec needs the SERVICE to have run this boot to have
anything to schedule from. Restarting the timer does not supply that; running the
service does, so the role now runs the check once after enabling. Also dropped
`Requires=fulcrum.service` from the timer - on a timer that means "stop watching
when the watched thing stops".

Diagnostic note: NextElapseUSecRealtime is always empty for a monotonic timer, so
it reads as broken even when healthy. I misread it once and wrongly called the
timer dead. Use NextElapseUSecMonotonic or systemctl list-timers.

fulcrum_ssl_port and fulcrum_tailscale_hostname moved to services_config.yml -
the socket-proxy play on the edge host needs them and a role default cannot reach
a second play.

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

ansible/roles/fulcrum/tasks/install.yml

@@ -0,0 +1,146 @@
+---
+- name: Calculate db_mem as a share of system RAM
+  set_fact:
+    fulcrum_db_mem_mb: "{{ (ansible_memtotal_mb | float * fulcrum_db_mem_percent) | int }}"
+  when: fulcrum_db_mem_mb_override | string | length == 0
+
+- name: Use the explicit db_mem override
+  set_fact:
+    fulcrum_db_mem_mb: "{{ fulcrum_db_mem_mb_override }}"
+  when: fulcrum_db_mem_mb_override | string | length > 0
+  changed_when: false
+
+- name: Display calculated db_mem value
+  debug:
+    msg: "Setting db_mem to {{ fulcrum_db_mem_mb }} MB ({{ (fulcrum_db_mem_percent * 100) | int }}% of {{ ansible_memtotal_mb }} MB total RAM)"
+
+- name: Display Fulcrum version to install
+  debug:
+    msg: "Installing Fulcrum version {{ fulcrum_version }}"
+
+- name: Install required packages
+  apt:
+    name:
+      - curl
+      - wget
+      - openssl
+    state: present
+    update_cache: yes
+
+- name: Create fulcrum group
+  group:
+    name: "{{ fulcrum_group }}"
+    system: yes
+    state: present
+
+- name: Create fulcrum user
+  user:
+    name: "{{ fulcrum_user }}"
+    group: "{{ fulcrum_group }}"
+    system: yes
+    shell: /usr/sbin/nologin
+    home: /home/{{ fulcrum_user }}
+    create_home: yes
+    state: present
+
+- name: Create Fulcrum database directory (heavy data on special mount)
+  file:
+    path: "{{ fulcrum_db_dir }}"
+    state: directory
+    owner: "{{ fulcrum_user }}"
+    group: "{{ fulcrum_group }}"
+    mode: '0755'
+
+- name: Create Fulcrum config directory
+  file:
+    path: "{{ fulcrum_config_dir }}"
+    state: directory
+    owner: root
+    group: "{{ fulcrum_group }}"
+    mode: '0755'
+
+- name: Create Fulcrum lib directory (for banner and other data files)
+  file:
+    path: "{{ fulcrum_lib_dir }}"
+    state: directory
+    owner: "{{ fulcrum_user }}"
+    group: "{{ fulcrum_group }}"
+    mode: '0755'
+
+# ===========================================
+# SSL Certificate Generation
+# ===========================================
+- name: Check if SSL certificate already exists
+  stat:
+    path: "{{ fulcrum_ssl_cert_path }}"
+  register: fulcrum_ssl_cert_exists
+  when: fulcrum_ssl_enabled | default(false)
+
+- name: Generate self-signed SSL certificate for Fulcrum
+  command: >
+    openssl req -x509 -newkey rsa:4096
+    -keyout {{ fulcrum_ssl_key_path }}
+    -out {{ fulcrum_ssl_cert_path }}
+    -sha256 -days {{ fulcrum_ssl_cert_days }}
+    -nodes
+    -subj "/C=XX/ST=Decentralized/L=Bitcoin/O=Fulcrum/OU=Electrum/CN=fulcrum.local"
+  args:
+    creates: "{{ fulcrum_ssl_cert_path }}"
+  when: fulcrum_ssl_enabled | default(false)
+  notify: Restart fulcrum
+
+- name: Set SSL certificate permissions
+  file:
+    path: "{{ fulcrum_ssl_cert_path }}"
+    owner: "{{ fulcrum_user }}"
+    group: "{{ fulcrum_group }}"
+    mode: '0644'
+  when: fulcrum_ssl_enabled | default(false) and fulcrum_ssl_cert_exists.stat.exists | default(false) or fulcrum_ssl_enabled | default(false)
+
+- name: Set SSL key permissions
+  file:
+    path: "{{ fulcrum_ssl_key_path }}"
+    owner: "{{ fulcrum_user }}"
+    group: "{{ fulcrum_group }}"
+    mode: '0600'
+  when: fulcrum_ssl_enabled | default(false)
+
+- name: Check if Fulcrum binary already exists
+  stat:
+    path: "{{ fulcrum_binary_path }}"
+  register: fulcrum_binary_exists
+  changed_when: false
+
+- name: Download Fulcrum binary tarball
+  get_url:
+    url: "https://github.com/cculianu/Fulcrum/releases/download/v{{ fulcrum_version }}/Fulcrum-{{ fulcrum_version }}-x86_64-linux.tar.gz"
+    dest: "/tmp/Fulcrum-{{ fulcrum_version }}-x86_64-linux.tar.gz"
+    mode: '0644'
+  when: not fulcrum_binary_exists.stat.exists
+
+- name: Extract Fulcrum binary
+  unarchive:
+    src: "/tmp/Fulcrum-{{ fulcrum_version }}-x86_64-linux.tar.gz"
+    dest: "/tmp"
+    remote_src: yes
+  when: not fulcrum_binary_exists.stat.exists
+
+- name: Install Fulcrum binary
+  copy:
+    src: "/tmp/Fulcrum-{{ fulcrum_version }}-x86_64-linux/Fulcrum"
+    dest: "{{ fulcrum_binary_path }}"
+    owner: root
+    group: root
+    mode: '0755'
+    remote_src: yes
+  when: not fulcrum_binary_exists.stat.exists
+
+- name: Verify Fulcrum binary installation
+  command: "{{ fulcrum_binary_path }} --version"
+  register: fulcrum_version_check
+  changed_when: false
+
+- name: Display Fulcrum version
+  debug:
+    msg: "{{ fulcrum_version_check.stdout_lines }}"
+