chore: add husky pre-commit hook and lint-staged configuration

- Created a pre-commit hook in .husky to run lint-staged.
- Added .lintstagedrc.mjs to format frontend files with Prettier and apply Spotless to backend Java files.
- Introduced .prettierignore to exclude specific directories from formatting.

frontend/src/app/services/http-error-message.ts

@@ -1,11 +1,11 @@
 export function httpErrorMessage(error: unknown, fallback: string): string {
-  return typeof error === 'object' &&
-    error !== null &&
-    'error' in error &&
-    typeof error.error === 'object' &&
-    error.error !== null &&
-    'message' in error.error &&
-    typeof error.error.message === 'string'
-    ? error.error.message
-    : fallback;
+	return typeof error === 'object' &&
+		error !== null &&
+		'error' in error &&
+		typeof error.error === 'object' &&
+		error.error !== null &&
+		'message' in error.error &&
+		typeof error.error.message === 'string'
+		? error.error.message
+		: fallback;
 }