Dashboard polish

Consistent tables. Every table in the dashboard now uses the same layout, the sidebar shows the workspace you are in, and a row on the incidents list opens the incident wherever you click it.

Redesigned sign-in pages. The sign-in, install and invite pages have been redesigned around a single form.

Reconnect Slack banner. If Firefight loses access to your Slack workspace, for example because the app was uninstalled, a banner appears on every dashboard page. Admins get a Reconnect Slack button, and everyone else is told to ask an admin. The dashboard keeps working in the meantime.