fix(host): derive template backup dir from config, drop hardcoded path (W2)

backup_template used a hardcoded _BACKUP_BASE_DIR=/var/lib/ci/backups; now derives <config.paths.root>/backups (matches the CLI --backup-base-dir default) per the plan's no-hardcoded-path gotcha. Tests no longer need to monkeypatch the constant.

plans/web-ui-management-plan.md

@@ -20,7 +20,7 @@ Stato passi (spunta man mano):
 
 - [x] **W0** — Scaffolding: extra `[web]` in `pyproject.toml`, dir package `operations/` + `web/`, skeleton test. Nessuna logica.
 - [x] **W1** — Layer `operations/vms.py`: estrai la logica da `commands/vm.py` in funzioni tipate che ritornano dataclass. Refactor dei comandi CLI per chiamarle. **Comportamento CLI invariato.** (Incluso: seam `VmBackend.list_running()` + fold del fix §2.8 IP-pool leak via `IpSlotPool.reconcile` / `operations.vms.reconcile_ip_leases`.)
-- [ ] **W2** — Layer `operations/cache.py` + `operations/host.py`: stato cache cargo, purge, disco, runner, backup template. Refactor `retention.py` / `monitor.py`.
+- [x] **W2** — Layer `operations/cache.py` + `operations/host.py`: stato cache cargo, purge, disco, runner, backup template. Refactor `retention.py` (`monitor.py` lasciato invariato — refactor opzionale; `disk_status`/`runner_status` verranno consumati dalla web app in W4).
 - [ ] **W3** — `operations/audit.py`: append-only JSONL + lettura. Config `[web]` in `config.py`.
 - [ ] **W4** — App web core: `web/app.py` factory + `commands/web.py` (`ci web serve`). Dashboard **read-only** (VM, cache, disco, runner). Ancora **senza auth**, bind localhost.
 - [ ] **W5** — Auth: Gitea OIDC (Authlib) + sessione firmata + allowlist utenti. Tutte le route protette.

src/ci_orchestrator/operations/host.py

@@ -10,8 +10,8 @@ every ``systemctl`` invocation is an argument list, read-only.
 
 ``backup_template`` reuses the archive-step shape from
 ``commands/template.py::template_backup`` (timestamped ``7z`` archive under
-``/var/lib/ci/backups``) but is a fresh, click-free implementation so this
+``<config.paths.root>/backups``) but is a fresh, click-free implementation so
-module has no dependency on the CLI layer.
+this module has no dependency on the CLI layer.
 """
 
 from __future__ import annotations
@@ -27,7 +27,6 @@ if TYPE_CHECKING:  # pragma: no cover
     from ci_orchestrator.config import Config
 
 _SYSTEMCTL_TIMEOUT = 10.0
-_BACKUP_BASE_DIR = Path("/var/lib/ci/backups")
 
 
 @dataclass(frozen=True)
@@ -141,14 +140,17 @@ def backup_template(config: Config, template: str, *, dry_run: bool = False) ->
             error=f"Template directory not found: {tmpl_dir}",
         )
 
+    # Backup dir is config-driven (mirrors the CLI's --backup-base-dir default
+    # of <root>/backups); no hardcoded host path.
+    backup_base = config.paths.root / "backups"
     timestamp = datetime.now(tz=UTC).strftime("%Y%m%d_%H%M%S")
-    archive_path = _BACKUP_BASE_DIR / f"Template_{template}_{timestamp}.7z"
+    archive_path = backup_base / f"Template_{template}_{timestamp}.7z"
 
     if dry_run:
         return BackupResult(template=template, archive_path=archive_path, ok=True, error=None)
 
     try:
-        _BACKUP_BASE_DIR.mkdir(parents=True, exist_ok=True)
+        backup_base.mkdir(parents=True, exist_ok=True)
         _compress_7z(tmpl_dir, archive_path)
     except (OSError, subprocess.CalledProcessError) as exc:
         return BackupResult(template=template, archive_path=None, ok=False, error=str(exc))

tests/python/test_operations_host.py

@@ -203,7 +203,6 @@ def test_backup_template_dry_run_does_not_compress(monkeypatch: pytest.MonkeyPat
     tmpl_dir = templates / "WinBuild2025"
     tmpl_dir.mkdir(parents=True)
     config = _make_config(templates)
-    monkeypatch.setattr(host_module, "_BACKUP_BASE_DIR", tmp_path / "backups")
 
     calls: list[tuple[Path, Path]] = []
     monkeypatch.setattr(host_module, "_compress_7z", lambda src, dst: calls.append((src, dst)))
@@ -225,7 +224,6 @@ def test_backup_template_success_mocked_archive_step(
     tmpl_dir = templates / "WinBuild2025"
     tmpl_dir.mkdir(parents=True)
     config = _make_config(templates)
-    monkeypatch.setattr(host_module, "_BACKUP_BASE_DIR", tmp_path / "backups")
 
     def _fake_compress(src: Path, dst: Path) -> None:
         dst.parent.mkdir(parents=True, exist_ok=True)
@@ -249,7 +247,6 @@ def test_backup_template_archive_failure_reported(
     tmpl_dir = templates / "WinBuild2025"
     tmpl_dir.mkdir(parents=True)
     config = _make_config(templates)
-    monkeypatch.setattr(host_module, "_BACKUP_BASE_DIR", tmp_path / "backups")
 
     def _boom(_src: Path, _dst: Path) -> None:
         raise subprocess.CalledProcessError(1, ["7z"])
@@ -269,7 +266,6 @@ def test_backup_template_never_calls_real_vmrun_or_7z(monkeypatch: pytest.Monkey
     tmpl_dir = templates / "WinBuild2025"
     tmpl_dir.mkdir(parents=True)
     config = _make_config(templates)
-    monkeypatch.setattr(host_module, "_BACKUP_BASE_DIR", tmp_path / "backups")
 
     called: list[bool] = []