feat: add Zod schema validation to patterns/detect route

- Import z from zod
- Add CandleSchema validating time, open, high, low, close (number), volume (optional number)
- Add PatternDetectRequestSchema validating candles array and patterns array of non-empty strings
- Use safeParse() and return HTTP 400 with error details on validation failure
- Forward only validated data to the inference service
- Mark task 4.5 as completed in tasks.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/api/patterns/detect/route.ts

@@ -1,9 +1,24 @@
 import { NextRequest, NextResponse } from 'next/server';
+import { z } from 'zod';
 
 const INFERENCE_API_URL = process.env.INFERENCE_API_URL || 'http://localhost:8001';
 // Pattern detection may take longer on large datasets
 const INFERENCE_API_TIMEOUT = parseInt(process.env.INFERENCE_API_TIMEOUT || '60000', 10);
 
+const CandleSchema = z.object({
+  time: z.number(),
+  open: z.number(),
+  high: z.number(),
+  low: z.number(),
+  close: z.number(),
+  volume: z.number().optional(),
+});
+
+const PatternDetectRequestSchema = z.object({
+  candles: z.array(CandleSchema),
+  patterns: z.array(z.string().min(1)),
+});
+
 export async function POST(request: NextRequest) {
   const controller = new AbortController();
   const timeoutId = setTimeout(() => controller.abort(), INFERENCE_API_TIMEOUT);
@@ -11,10 +26,21 @@ export async function POST(request: NextRequest) {
   try {
     const body = await request.json();
 
+    const result = PatternDetectRequestSchema.safeParse(body);
+    if (!result.success) {
+      clearTimeout(timeoutId);
+      return NextResponse.json(
+        { error: 'Invalid request', details: result.error.flatten() },
+        { status: 400 }
+      );
+    }
+
+    const validatedBody = result.data;
+
     const response = await fetch(`${INFERENCE_API_URL}/patterns/detect`, {
       method: 'POST',
       headers: { 'Content-Type': 'application/json', 'X-API-Key': process.env.API_KEY || '' },
-      body: JSON.stringify(body),
+      body: JSON.stringify(validatedBody),
       signal: controller.signal,
     });
     clearTimeout(timeoutId);