fix: synchronize runtime locales and harden online updates

Translate UI, scheduler, validation, preload and maintenance messages dynamically, and propagate locale changes between workers. Harden update checks, downloads and terminal states, verify Debian pnpm, and ignore generated test artifacts.

back/middlewares/validationErrors.ts

@@ -0,0 +1,18 @@
+import { errors, isCelebrateError } from 'celebrate';
+import { ErrorRequestHandler } from 'express';
+import { t } from '../shared/i18n';
+
+const respond = errors();
+
+// Schemas are compiled once at startup; resolve their messages per request so
+// changing the system language also changes errors from those existing schemas.
+const validationErrors: ErrorRequestHandler = (error, req, res, next) => {
+  if (isCelebrateError(error)) {
+    for (const detail of error.details.values()) {
+      detail.message = detail.details.map((item) => t(item.message)).join('. ');
+    }
+  }
+  return respond(error, req, res, next);
+};
+
+export default validationErrors;