chore: improve tooling, linting, testing, and CI

- Add LICENSE file (CC BY-NC-SA 4.0)
- Add .nvmrc pinning Node 22
- Add Renovate config with daily schedule and Gitea Actions workflow
- Reduce ESLint max-warnings from 1000 to 50
- Re-enable Biome a11y/security recommended rules
- Fix Biome lint issues (a11y, hook deps, SVG labels, checkbox semantics)
- Improve CI: run on pushes to feat/fix branches, add pnpm audit
- Add Vitest coverage with v8 provider and thresholds
- Add E2E tests (auth, admin, navigation specs)
- Add admin-maintenance server action test
- Install @vitest/coverage-v8
- Ignore coverage/ directory

e2e/auth.spec.ts

@@ -0,0 +1,32 @@
+import { expect, test } from "@playwright/test";
+
+test.describe("Authentication flows", () => {
+	test("login form validates required fields", async ({ page }) => {
+		await page.goto("/login");
+		await page.click('button[type="submit"]');
+		await expect(page.locator("text=required")).toBeVisible({ timeout: 5000 });
+	});
+
+	test("login with invalid credentials shows error", async ({ page }) => {
+		await page.goto("/login");
+		await page.fill('input[name="username"]', "nonexistent");
+		await page.fill('input[name="password"]', "wrongpassword");
+		await page.click('button[type="submit"]');
+		await expect(page.locator("text=invalid")).toBeVisible({ timeout: 5000 });
+	});
+
+	test("register page has password confirmation field", async ({ page }) => {
+		await page.goto("/register");
+		await expect(page.locator('input[name="confirmPassword"]')).toBeVisible();
+	});
+
+	test("register form validates password match", async ({ page }) => {
+		await page.goto("/register");
+		await page.fill('input[name="password"]', "Password123!");
+		await page.fill('input[name="confirmPassword"]', "DifferentPass123!");
+		await page.click('button[type="submit"]');
+		await expect(page.locator("text=match|komen overeen|kloppen")).toBeVisible({
+			timeout: 5000,
+		});
+	});
+});