test: Vitest setup + unit tests for API client, hooks, services + staff E2E

- Vitest + React Testing Library + MSW setup
- API client: 11 unit tests (fetch, errors, auth header, download, network failure)
- Service hooks: 26 tests across members, distributions, stock, dashboard, staff
- Custom hooks: 5 debounce tests (timer behavior, reset, custom delay)
- Components: 5 tests (offline banner, error boundary with retry)
- E2E: staff management page interactions
- npm scripts: test, test:run, test:coverage

cannamanage-frontend/package.json

@@ -14,6 +14,9 @@
     "lint": "next lint",
     "lint:fix": "next lint --fix",
     "format": "prettier --ignore-path .gitignore --write .",
+    "test": "vitest",
+    "test:run": "vitest run",
+    "test:coverage": "vitest run --coverage",
     "test:e2e": "playwright test e2e/full-check.spec.ts e2e/functional-flows.spec.ts",
     "test:system": "playwright test e2e/system-test.spec.ts",
     "test:all": "playwright test"
@@ -72,21 +75,27 @@
     "@playwright/test": "^1.60.0",
     "@tailwindcss/postcss": "4.0.17",
     "@tailwindcss/typography": "0.5.15",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
     "@types/eslint__eslintrc": "2.1.2",
     "@types/node": "20",
     "@types/react": "19.0.12",
     "@types/react-dom": "19.0.4",
+    "@vitejs/plugin-react": "^6.0.2",
     "eslint": "9.18.0",
     "eslint-config-next": "15.5.18",
     "eslint-config-prettier": "10.1.1",
     "eslint-plugin-prettier": "5.2.3",
+    "jsdom": "^29.1.1",
+    "msw": "^2.14.6",
     "playwright": "^1.60.0",
     "postcss": "8",
     "prettier": "3.5.3",
     "prettier-plugin-tailwindcss": "0.6.11",
     "tailwindcss": "4.1.3",
     "tw-animate-css": "1.2.5",
-    "typescript": "5"
+    "typescript": "5",
+    "vitest": "^4.1.8"
   },
   "overrides": {
     "@types/react": "19.0.12",