feat(AppConfig): iterate how apps are managed

- auth clients are always shared, cannot be disabled
- custom connections are enabled by default, can be disabled
- any existing connections can be reconnected regardless of its AppConfig or AppAuthClient states

packages/backend/vitest.config.js

@@ -16,10 +16,10 @@ export default defineConfig({
       include: ['**/src/models/**', '**/src/controllers/**'],
       thresholds: {
         autoUpdate: true,
-        statements: 93.41,
-        branches: 93.46,
-        functions: 95.95,
-        lines: 93.41,
+        statements: 95.16,
+        branches: 94.66,
+        functions: 97.65,
+        lines: 95.16,
       },
     },
   },