dsh-session-theme: Show All Session Themes in the Sidebar

The DSH Web plugin `dsh-session-theme` is designed to address the issue where cold sessions in the sidebar only show folder names without displaying session themes. By prewarming the projection cache at startup, the plugin ensures that session themes are available as soon as the page loads. It features fault-tolerant handling, idempotent writes, and zero external dependencies. After installation, perform a hard refresh and confirm successful prewarming in the logs to improve the clarity of session presentation in the sidebar.