test(apps/app): set up Vitest harness — closes TECH-APP-VITEST (WS-6)

Mirrors apps/portal's Vitest setup so the SPA can take frontend
unit + component tests. Required prerequisite for WS-6 sessie 3b's
admin UI work — apps/portal had 113+ tests, apps/app had zero, and
launching WS-6's organizer UI uncovered while the portal SPA is
well-tested would be asymmetric quality.

Setup:
- vitest, happy-dom, @vue/test-utils, @testing-library/vue installed
- vitest.config.ts mirrors portal config: trimmed auto-imports
  (no pinia/vue-router/vue-i18n/@vueuse/math) so tests run fast
  in happy-dom without loading the full Vuexy bundle
- AutoImport's dts:false prevents the trimmed test-only set from
  clobbering the dev-server's full auto-imports.d.ts (apps/app's
  auto-import surface is bigger than the portal's)
- tests/setup.ts mocks vue-router by default; tests that exercise
  the real router can override per-suite
- Sample sanity test confirms the harness works end-to-end

Adds `pnpm test` and `pnpm test:watch` scripts to package.json.

Refs: BACKLOG TECH-APP-VITEST, WS-6 sessie 3b prerequisite

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/app/vitest.config.ts

@@ -0,0 +1,37 @@
+import { fileURLToPath } from 'node:url'
+import vue from '@vitejs/plugin-vue'
+import AutoImport from 'unplugin-auto-import/vite'
+import { defineConfig } from 'vitest/config'
+
+// Dedicated Vitest config — intentionally trimmed down from vite.config.ts.
+// Skip Vuetify / MetaLayouts / VueRouter plugins so unit tests run fast in
+// happy-dom without loading the full Vuexy bundle. Mirrors apps/portal/vitest.config.ts.
+export default defineConfig({
+  plugins: [
+    vue(),
+    AutoImport({
+      imports: ['vue', '@vueuse/core'],
+      dirs: ['./src/@core/utils', './src/@core/composable/', './src/composables/', './src/utils/'],
+      vueTemplate: true,
+      // Don't write to auto-imports.d.ts — vite.config.ts owns that file
+      // with the full app's auto-import set. Trimmed test-only set must
+      // not clobber the IDE typings for the running dev server.
+      dts: false,
+    }),
+  ],
+  resolve: {
+    alias: {
+      '@': fileURLToPath(new URL('./src', import.meta.url)),
+      '@core': fileURLToPath(new URL('./src/@core', import.meta.url)),
+      '@layouts': fileURLToPath(new URL('./src/@layouts', import.meta.url)),
+      '@images': fileURLToPath(new URL('./src/assets/images/', import.meta.url)),
+      '@styles': fileURLToPath(new URL('./src/assets/styles/', import.meta.url)),
+    },
+  },
+  test: {
+    environment: 'happy-dom',
+    globals: true,
+    include: ['tests/**/*.{test,spec}.ts', 'src/**/__tests__/**/*.{test,spec}.ts'],
+    setupFiles: ['./tests/setup.ts'],
+  },
+})