langfuse-integration

Replaces Phoenix observability with Langfuse Cloud (EU) traceability for pharmaceutical test generation. Adds @observe decorators to existing code, configures LlamaIndex callbacks, propagates GAMP-5 compliance attributes, and removes Phoenix dependencies. Use PROACTIVELY when implementing Task 2.3 (LangFuse setup), migrating observability systems, or ensuring ALCOA+ trace attribution. MUST BE USED for pharmaceutical compliance monitoring requiring persistent cloud storage.