Add read-only web dashboard MVP

Adds a disabled-by-default loopback web dashboard MVP with read-only control-plane views, prompt preview redaction, Vite React UI, and validation coverage.

src/config.ts

@@ -141,6 +141,7 @@ export const STATUS_SHOW_ROOMS = CONFIG.status.showRooms;
 export const STATUS_SHOW_ROOM_DETAILS = CONFIG.status.showRoomDetails;
 export const USAGE_DASHBOARD_ENABLED = CONFIG.status.usageDashboardEnabled;
 export const CODEX_WARMUP_CONFIG = CONFIG.codexWarmup;
+export const WEB_DASHBOARD = CONFIG.webDashboard;
 
 // Timezone for scheduled tasks (cron expressions, etc.)
 // Uses system timezone by default