test(e2e): add Playwright smoke tests for catalog, inventory, checkout, auth

- catalog.spec.js: brand grid loads, search interaction
- inventory.spec.js: table loads, detail modal opens
- pos-checkout.spec.js: cart visible, catalog search from POS
- auth-guard.spec.js: unauthenticated redirect to login

tests/e2e/inventory.spec.js

@@ -0,0 +1,21 @@
+const { test, expect } = require('@playwright/test');
+
+test.describe('Nexus POS — Inventory', () => {
+  test('inventory page loads with table or grid', async ({ page }) => {
+    await page.goto('/pos/inventory');
+    await expect(page.locator('#inventoryTable, .data-table, #partsGrid, .grid, table')).toBeVisible({ timeout: 10000 });
+    const content = await page.locator('body').textContent();
+    expect(content).toMatch(/inventario|stock|producto|parte/i);
+  });
+
+  test('product detail modal or panel opens', async ({ page }) => {
+    await page.goto('/pos/inventory');
+    // Try clicking first row or card
+    const firstRow = page.locator('.data-table tbody tr, .grid .card, .inventory-row').first();
+    await firstRow.waitFor({ state: 'visible', timeout: 10000 }).catch(() => {});
+    if (await firstRow.isVisible().catch(() => false)) {
+      await firstRow.click();
+      await expect(page.locator('.modal, .detail-panel, #detailPanel, [role="dialog"]')).toBeVisible({ timeout: 5000 });
+    }
+  });
+});