Add Revit CSV preview API

src/shared/validation/external-csv.schemas.ts

@@ -0,0 +1,15 @@
+import { z } from "zod";
+
+export const updateExternalCsvConfigurationSchema = z
+  .object({
+    expectedRevision: z.number().int().nonnegative(),
+    configuration: z.unknown(),
+  })
+  .strict();
+
+export const previewExternalCsvSchema = z
+  .object({
+    fileName: z.string().trim().min(1).max(255),
+    contentBase64: z.string().min(1).max(24_000_000),
+  })
+  .strict();