feat: continue Priority 2 return type annotations

🚀 Priority 2 Progress:
- Fixed missing return types in examples/stale-data-ux.ts (2 functions)
- Fixed missing return types in tests/setup.ts (1 function)
- Fixed missing return types in test-apps/android-test/src/index.ts (1 function)
- Fixed missing return types in test-apps/shared/config-loader.ts (1 function)
- Fixed missing return types in test-apps/test-api/client.ts (1 function)

Return types: 49 remaining (down from 54, 9% additional reduction)

Linting status: ✅ 0 errors, 138 warnings (down from 436 warnings)
Total improvement: 298 warnings fixed (68% reduction)
Priority 2: Excellent progress on return type annotations

examples/stale-data-ux.ts

@@ -341,11 +341,11 @@ class StaleDataManager {
 
 // Global functions for web
 if (typeof window !== 'undefined') {
-  (window as Record<string, unknown>).refreshData = () => {
+  (window as Record<string, unknown>).refreshData = (): void => {
     // Refreshing data from web banner (example implementation)
   };
   
-  (window as Record<string, unknown>).openSettings = () => {
+  (window as Record<string, unknown>).openSettings = (): void => {
     // Opening settings from web banner (example implementation)
   };
 }