refactor: remove Workers AI as any with proper type definitions

- Add WorkersAIModel, WorkersAITextGenerationInput/Output types
- Remove `as any` from summary-service.ts (4 instances)
- Remove `as any` from bank-sms-parser.ts (3 instances)
- Remove `as any` from n8n-service.ts (2 instances)
- Add OpenAIResponse interface for API responses

Type-safe Workers AI calls with full IntelliSense support.

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

src/n8n-service.ts

@@ -1,5 +1,5 @@
 import { z } from 'zod';
-import { Env, IntentAnalysis, N8nResponse } from './types';
+import { Env, IntentAnalysis, N8nResponse, WorkersAITextGenerationOutput, WorkersAITextGenerationInput } from './types';
 import { createLogger } from './utils/logger';
 
 const logger = createLogger('n8n-service');
@@ -53,10 +53,14 @@ ${userMessage}
 JSON:`;
 
   try {
-    const response = await ai.run('@cf/meta/llama-3.1-8b-instruct' as any, {
+    const input: WorkersAITextGenerationInput = {
       messages: [{ role: 'user', content: prompt }],
       max_tokens: 100,
-    }) as any;
+    };
+    const response = await ai.run(
+      '@cf/meta/llama-3.1-8b-instruct' as '@cf/meta/llama-3.1-8b-instruct-fp8',
+      input
+    ) as WorkersAITextGenerationOutput;
 
     const text = response.response || '';