Increase Jest coverage thresholds to enforce higher test quality

frontend/jest.config.js

@@ -31,10 +31,10 @@ const customJestConfig = {
   ],
   coverageThreshold: {
     global: {
-      branches: 70,
+      branches: 85,
-      functions: 70,
+      functions: 85,
-      lines: 70,
+      lines: 90,
-      statements: 70,
+      statements: 90,
     },
   },
 }