test: ensure kv global is always available

This is comitted separately from the commit for AppService.comp.test.js
that will follow because it interacts with all other test cases. It did
not cause any issue based on what I observed, but I'm still wrapping it
in a separate commit in case we need to revert or change it later.

src/backend/vitest.config.ts

@@ -5,7 +5,7 @@ import { defineConfig } from 'vitest/config';
 export default defineConfig(({ mode }) => ({
     test: {
         globals: true,
-        setupFiles: [],
+        setupFiles: ['./vitest.setup.js'],
         coverage: {
             provider: 'v8',
             reporter: ['text', 'json', 'json-summary', 'html', 'lcov'],

src/backend/vitest.setup.js

@@ -0,0 +1,5 @@
+// Vitest setup file - runs before all test files
+// Initializes globalThis.kv which is required by PermissionService and other services
+
+import { kv } from './src/util/kvSingleton';
+globalThis.kv = kv;