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

biome.json

@@ -7,7 +7,7 @@
 	},
 	"files": {
 		"ignoreUnknown": false,
-		"includes": ["**", "!setup", "!public", "!*.cjs"]
+		"includes": ["**", "!setup", "!*.cjs", "!coverage"]
 	},
 	"formatter": {
 		"enabled": true,
@@ -23,9 +23,6 @@
 			"performance": {
 				"noImgElement": "off"
 			},
-			"a11y": {
-				"noLabelWithoutControl": "off"
-			},
 			"style": {
 				"noDescendingSpecificity": "off"
 			}