feat: Windows admin in Settings UI and WinRM host test (0.10.1)

Store domain admin in ui_settings (DB overrides env); qwinsta/logoff use effective config.
Host card: POST /hosts/{id}/actions/winrm-test via pywinrm.

backend/app/api/v1/hosts.py

@@ -10,6 +10,14 @@ from app.models import Event, Host
 from app.schemas.list_models import HostDetail, HostListResponse, HostSummary
 from app.services.agent_version import latest_agent_versions_by_product
 from app.services.host_delete import delete_host_and_related
+from app.services.win_admin_settings import get_effective_win_admin_config
+from app.services.winrm_connect import (
+    HostNotWindowsError,
+    HostTargetMissingError,
+    WinAdminNotConfiguredError,
+    resolve_windows_host_target,
+    test_winrm_connection,
+)
 from app.services.host_health import (
     HEARTBEAT_TYPE,
     agent_status as compute_agent_status,
@@ -156,6 +164,53 @@ class HostDeleteResponse(BaseModel):
     deleted_problems: int
 
 
+class HostWinRmTestResponse(BaseModel):
+    ok: bool
+    message: str
+    target: str
+    hostname: str | None = None
+
+
+@router.post("/{host_id}/actions/winrm-test", response_model=HostWinRmTestResponse)
+def test_host_winrm(
+    host_id: int,
+    db: Session = Depends(get_db),
+    _user=Depends(require_admin),
+) -> HostWinRmTestResponse:
+    host = db.get(Host, host_id)
+    if host is None:
+        raise HTTPException(status_code=404, detail="Host not found")
+
+    cfg = get_effective_win_admin_config(db)
+    if not cfg.configured:
+        raise HTTPException(status_code=400, detail="Windows domain admin is not configured")
+
+    try:
+        target = resolve_windows_host_target(host)
+    except HostNotWindowsError as exc:
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
+    except HostTargetMissingError as exc:
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
+
+    try:
+        result = test_winrm_connection(
+            target=target,
+            user=cfg.user,
+            password=cfg.password,
+        )
+    except WinAdminNotConfiguredError as exc:
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
+    except RuntimeError as exc:
+        raise HTTPException(status_code=503, detail=str(exc)) from exc
+
+    return HostWinRmTestResponse(
+        ok=result.ok,
+        message=result.message,
+        target=result.target,
+        hostname=result.hostname,
+    )
+
+
 @router.delete("/{host_id}", response_model=HostDeleteResponse)
 def delete_host(
     host_id: int,