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

vitest.config.ts

@@ -19,5 +19,24 @@ export default defineConfig({
 		// unit tests run without a populated .env.
 		env: { SKIP_ENV_VALIDATION: "1" },
 		exclude: ["e2e/**", "node_modules/**", ".next/**"],
+		coverage: {
+			enabled: true,
+			provider: "v8",
+			reporter: ["text", "lcov", "html"],
+			thresholds: {
+				statements: 5,
+				branches: 3,
+				functions: 4,
+				lines: 5,
+			},
+			include: ["src/**/*.{ts,tsx}"],
+			exclude: [
+				"src/generated/**",
+				"src/**/*.test.ts",
+				"src/**/*.test.tsx",
+				"src/types/**",
+				"src/test/**",
+			],
+		},
 	},
 });