Clean up dead demos and restructure directory layout

Phase 1 - Remove dead/duplicate content:
- Delete demos/samples_java/ (incomplete Java demo)
- Delete demos/shared/chatbot_ui/ (replaced by AnythingLLM)
- Delete demos/shared/grafana/, prometheus/, logfire/, honeycomb/, signoz/
  (legacy observability stacks; only jaeger is retained)
- Delete variant docker-compose files (honeycomb, logfire, signoz, jaeger)
- Delete demos/use_cases/spotify_bearer_auth/run_demo.sh (stale script)

Phase 2 - Restructure into semantic categories:
- getting_started/  : weather_forecast, llm_gateway
- agent_orchestration/ : travel_agents, multi_agent_crewai_langchain
- llm_routing/       : model_alias_routing, preference_based_routing, claude_code_router
- filter_chains/     : http_filter, mcp_filter
- integrations/      : ollama, spotify_bearer_auth
- advanced/          : model_choice_test_harness, multi_turn_rag,
                       currency_exchange, stock_quote

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

demos/samples_python/multi_turn_rag_agent/docker-compose.yaml

@@ -1,24 +0,0 @@
-services:
-  rag_energy_source_agent:
-    build:
-      context: .
-      dockerfile: Dockerfile
-    ports:
-      - "18083:80"
-    healthcheck:
-        test: ["CMD", "curl" ,"http://localhost:80/healthz"]
-        interval: 5s
-        retries: 20
-
-  chatbot_ui:
-    build:
-      context: ../../shared/chatbot_ui
-      dockerfile: Dockerfile
-    ports:
-      - "18080:8080"
-    environment:
-      - CHAT_COMPLETION_ENDPOINT=http://host.docker.internal:10000/v1
-    extra_hosts:
-      - "host.docker.internal:host-gateway"
-    volumes:
-      - ./config.yaml:/app/plano_config.yaml