feat: add AI enrichment service with Claude Haiku and rule-based fallback

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

src/ai/ai.module.ts

@@ -0,0 +1,8 @@
+import { Module } from '@nestjs/common';
+import { AiEnrichmentService } from './ai-enrichment.service';
+
+@Module({
+    providers: [AiEnrichmentService],
+    exports: [AiEnrichmentService],
+})
+export class AiModule {}