feat: css editor (#1542)

* feat: allow editing CSS from settings

---------

Co-authored-by: Carlos Valente <carlosvalente@pm.me>

refactor: style tweaks

apps/server/src/api-data/assets/assets.validation.ts

@@ -0,0 +1,12 @@
+import { Request, Response, NextFunction } from 'express';
+import { body, validationResult } from 'express-validator';
+
+export const validatePostCss = [
+  body('css').exists().isString().trim(),
+
+  (req: Request, res: Response, next: NextFunction) => {
+    const errors = validationResult(req);
+    if (!errors.isEmpty()) return res.status(422).json({ errors: errors.array() });
+    next();
+  },
+];