CREATE TABLE activity_log (
    id           INTEGER PRIMARY KEY AUTOINCREMENT,
    host_id      INTEGER NOT NULL REFERENCES hosts(id) ON DELETE CASCADE,
    operation_id INTEGER REFERENCES operations(id) ON DELETE SET NULL,
    level        TEXT NOT NULL DEFAULT 'info',
    message      TEXT NOT NULL,
    source       TEXT NOT NULL DEFAULT '',
    created_at   TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ','now'))
);
CREATE INDEX idx_activity_host ON activity_log(host_id, created_at DESC);