fix(ai-assistant): infer response types from Zod schemas

src/modules/ai-assistant/ai-assistant.service.ts

 import { Prisma, TransactionType } from '@prisma/client';
+import { z } from 'zod';
 import { getAIProvider } from '../../common/ai/ai-provider.factory';
 import {
   AIContentPart,
@@ -37,7 +38,6 @@ import {
   receiptResponseSchema,
   recommendationsResponseSchema,
 } from './ai-assistant-response.validation';
-import type { AIResponseValidator } from './ai-assistant-response.validation';
 
 const MILLISECONDS_PER_DAY = 24 * 60 * 60 * 1000;
 const DEFAULT_CONTEXT_DAYS = 90;
@@ -227,12 +227,12 @@ export class AIAssistantService {
     );
   }
 
-  private async generateWithContext<T>(
+  private async generateWithContext<TSchema extends z.ZodTypeAny>(
     context: ResolvedContext,
     prompt: string,
     responseJsonSchema: Record<string, unknown>,
-    outputSchema: AIResponseValidator<T>,
-  ): Promise<AIServiceResult<T>> {
+    outputSchema: TSchema,
+  ): Promise<AIServiceResult<z.output<TSchema>>> {
     const response = await this.generate(
       {
         systemInstruction: SYSTEM_INSTRUCTION,
@@ -259,9 +259,9 @@ export class AIAssistantService {
     };
   }
 
-  private async generate<T>(
+  private async generate<TSchema extends z.ZodTypeAny>(
     request: AIGenerateRequest,
-    outputSchema: AIResponseValidator<T>,
+    outputSchema: TSchema,
   ) {
     try {
       const response = await getAIProvider().generateStructured(request);