fix: add beta_mode property to SystemConfig interface

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Co-Authored-By: tinkle-community <tinklefund@gmail.com>

web/src/lib/config.ts

@@ -1,5 +1,6 @@
 export interface SystemConfig {
   admin_mode: boolean;
+  beta_mode: boolean;
 }
 
 let configPromise: Promise<SystemConfig> | null = null;