fix: Add pricingTiers to service Zod validators

- pricingTiers field was missing from createServiceSchema
- pricingTiers field was missing from updateServiceSchema
- This caused the field to be stripped during validation

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

src/validators/crm.validators.js

@@ -205,11 +205,13 @@ export const createServiceSchema = z.object({
       required_error: 'Cena je povinná',
     })
     .min(1, 'Cena nemôže byť prázdna'),
+  pricingTiers: z.string().optional().or(z.literal('').or(z.null())),
   description: z.string().max(1000).optional(),
 });
 
 export const updateServiceSchema = z.object({
   name: z.string().min(1).max(255).optional(),
   price: z.string().min(1).optional(),
+  pricingTiers: z.string().optional().or(z.literal('').or(z.null())),
   description: z.string().max(1000).optional().or(z.literal('').or(z.null())),
 });