refactor: Move inline Zod schemas from routes to validator files

Create ai-kurzy.validators.js and service.validators.js with schemas
extracted from their respective route files. Routes now import schemas
instead of defining them inline.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/validators/service.validators.js

@@ -0,0 +1,22 @@
+import { z } from 'zod';
+
+export const serviceIdSchema = z.object({
+  serviceId: z.string().uuid(),
+});
+
+export const folderIdSchema = z.object({
+  folderId: z.string().uuid(),
+});
+
+export const folderDocumentIdSchema = z.object({
+  folderId: z.string().uuid(),
+  documentId: z.string().uuid(),
+});
+
+export const createFolderSchema = z.object({
+  name: z.string().min(1).max(255),
+});
+
+export const updateFolderSchema = z.object({
+  name: z.string().min(1).max(255),
+});