feat: Set up JavaScript testing framework (Vitest + Playwright)

- Created package.json with Vitest and Playwright dependencies
- Configured vitest.config.js with happy-dom environment
- Configured playwright.config.js with Chromium browser
- Created test directory structure (tests/frontend/unit and e2e)
- Added setup.test.js with 10 Vitest validation tests
- Added setup.spec.js with 6 Playwright E2E validation tests
- Created FRONTEND_SETUP.md with Node.js installation guide
- Updated instructions.md marking task complete

Note: Requires Node.js installation before running tests

FRONTEND_SETUP.md

@@ -0,0 +1,136 @@
+# Frontend Testing Setup Guide
+
+## Prerequisites
+
+The frontend testing framework requires Node.js and npm to be installed.
+
+## 🔧 Installing Node.js and npm
+
+### Option 1: Using apt (Ubuntu/Debian)
+
+```bash
+sudo apt update
+sudo apt install nodejs npm
+```
+
+### Option 2: Using nvm (Recommended)
+
+```bash
+# Install nvm
+curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.0/install.sh | bash
+
+# Reload shell configuration
+source ~/.bashrc
+
+# Install latest LTS version of Node.js
+nvm install --lts
+
+# Verify installation
+node --version
+npm --version
+```
+
+### Option 3: Using conda
+
+```bash
+# Install Node.js in your conda environment
+conda install -c conda-forge nodejs
+
+# Verify installation
+node --version
+npm --version
+```
+
+## 📦 Installing Dependencies
+
+Once Node.js and npm are installed:
+
+```bash
+# Navigate to project root
+cd /home/lukas/Volume/repo/AniworldMain
+
+# Install all dependencies from package.json
+npm install
+
+# Install Playwright browsers (required for E2E tests)
+npm run playwright:install
+```
+
+## ✅ Verify Setup
+
+### Test Vitest (Unit Tests)
+
+```bash
+npm test
+```
+
+Expected output:
+```
+✓ tests/frontend/unit/setup.test.js (10 tests)
+  ✓ Vitest Setup Validation (4 tests)
+  ✓ DOM Manipulation Tests (6 tests)
+
+Test Files  1 passed (1)
+Tests  10 passed (10)
+```
+
+### Test Playwright (E2E Tests)
+
+**Important**: The FastAPI server must be running for E2E tests.
+
+```bash
+# Option 1: Let Playwright start the server automatically
+npm run test:e2e
+
+# Option 2: Start server manually in another terminal
+# Terminal 1:
+npm run start
+
+# Terminal 2:
+npm run test:e2e
+```
+
+Expected output:
+```
+Running 6 tests using 1 worker
+
+  ✓ tests/frontend/e2e/setup.spec.js:9:5 › Playwright Setup Validation › should load the home page
+  ✓ tests/frontend/e2e/setup.spec.js:19:5 › Playwright Setup Validation › should have working navigation
+  ...
+
+6 passed (6s)
+```
+
+## 🔍 Troubleshooting
+
+### Error: "Cannot find module 'vitest'"
+
+Run `npm install` to install dependencies.
+
+### Error: "Playwright browsers not installed"
+
+Run `npm run playwright:install`.
+
+### E2E Tests Timeout
+
+Ensure the FastAPI server is running and accessible at http://127.0.0.1:8000.
+
+Check if the server is running:
+```bash
+curl http://127.0.0.1:8000
+```
+
+### Port Already in Use
+
+If port 8000 is already in use, stop the existing server or change the port in `playwright.config.js`.
+
+## 📚 Next Steps
+
+After setup is complete, you can:
+
+1. Run unit tests: `npm test`
+2. Run E2E tests: `npm run test:e2e`
+3. View coverage: `npm run test:coverage` then open `htmlcov_frontend/index.html`
+4. Write new tests in `tests/frontend/unit/` or `tests/frontend/e2e/`
+
+See [tests/frontend/README.md](tests/frontend/README.md) for detailed testing documentation.