chore(backend): add vitest.config.ts

backend/vitest.config.ts

@@ -0,0 +1,12 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    include: ['src/**/*.test.ts'],
+    passWithNoTests: true,
+    env: {
+      ALLOW_ANONYMOUS_DEV: 'true',
+    },
+  },
+});