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/alembic/versions/017_ui_settings_win_admin.py

@@ -0,0 +1,25 @@
+"""ui_settings: Windows domain admin for agent commands
+
+Revision ID: 017
+Revises: 016
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "017"
+down_revision: Union[str, None] = "016"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column("ui_settings", sa.Column("win_admin_user", sa.String(256), nullable=True))
+    op.add_column("ui_settings", sa.Column("win_admin_password", sa.Text(), nullable=True))
+
+
+def downgrade() -> None:
+    op.drop_column("ui_settings", "win_admin_password")
+    op.drop_column("ui_settings", "win_admin_user")