Reduce to 2 concurrent batches to avoid Haiku output TPM bursting

3 concurrent batches hit the rate limit simultaneously then retry in
unison, causing repeated 429s. 2 concurrent keeps output rate lower.

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

src/PowderCoating.Infrastructure/Services/AiCatalogPriceCheckService.cs

@@ -22,7 +22,7 @@ public class AiCatalogPriceCheckService : IAiCatalogPriceCheckService
 
     private const string Model = "claude-haiku-4-5-20251001";
     private const int BatchSize = 25;
-    private const int MaxConcurrentBatches = 3; // Haiku has generous rate limits; retry logic handles any 429s
+    private const int MaxConcurrentBatches = 2; // 3 concurrent bursts past Haiku's output TPM limit
     private const int RateLimitRetrySeconds = 65; // wait just past the 60s window before retrying a 429
 
     private static readonly JsonSerializerOptions JsonOpts = new() { PropertyNameCaseInsensitive = true };