feat(semaphore): rewrite role with rootful Podman Quadlet + PostgreSQL

Complete rewrite of the semaphore role. Supersedes three prior
iterations whose admin-user-creation logic was unreliable across
Semaphore CLI versions.

Architecture:
  - Rootful Podman Quadlet under /etc/containers/systemd/
  - Separate PostgreSQL 16-alpine container on a user-defined
    podman network (semaphore-net)
  - Named volumes for both data stores (semaphore_data,
    semaphore_postgres_data) so container recreation is
    non-destructive
  - Pinned image tags: semaphoreui/semaphore:v2.18.5-ansible2.16.5
    and postgres:16-alpine
  - Post-deploy HTTP health check fails the playbook if Semaphore
    doesn't respond on /api/ping within ~60s

Admin user creation remains intentionally manual after first deploy;
the role README documents the exact podman exec command.

Removes the duplicate deploy_semaphore.yml and the now-unneeded
cleanup_semaphore.yml; day1_deploy_semaphore.yml is the canonical
entry point.

ansible/roles/semaphore/tasks/network.yml

@@ -0,0 +1,21 @@
+---
+# ============================================================================
+# Podman network
+# ----------------------------------------------------------------------------
+# Quadlet supports .network files, but for a single user-defined network
+# we keep it simple with an idempotent podman CLI invocation. The network
+# survives container removal; only re-created if missing.
+# ============================================================================
+
+- name: Check if semaphore network exists
+  ansible.builtin.command:
+    cmd: "podman network exists {{ semaphore_network_name }}"
+  register: semaphore_network_check
+  failed_when: false
+  changed_when: false
+
+- name: Create semaphore podman network
+  ansible.builtin.command:
+    cmd: "podman network create {{ semaphore_network_name }}"
+  when: semaphore_network_check.rc != 0
+  changed_when: true