Fix backend issues in desktop app (#4995)

# Description of Changes
Fixes two distinct but related issues in the backend of the desktop app:
- Correctly shows tools as unavaialable when the backend doesn't have
the dependencies or has disabled them etc. (same as web version - this
primarily didn't work on desktop because the app spawns before the
backend is running)
- Fixes infinite re-rendering issues caused by the app polling whether
the backend is healthy or not

frontend/src/core/contexts/AppConfigContext.tsx

@@ -42,6 +42,7 @@ export interface AppConfig {
   appVersion?: string;
   machineType?: string;
   activeSecurity?: boolean;
+  dependenciesReady?: boolean;
   error?: string;
 }