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/weather_forecast/Dockerfile

@@ -1,40 +0,0 @@
-# Blazing fast Python Docker builds with uv
-
-# The builder image, used to build the virtual environment
-FROM python:3.12 as builder
-
-# Install uv
-RUN pip install --no-cache-dir uv
-
-# Set working directory
-WORKDIR /code
-
-# Copy dependency files
-COPY pyproject.toml uv.lock ./
-RUN touch README.md
-
-# Install dependencies using uv
-RUN uv sync --frozen --no-dev
-
-# The runtime image, used to just run the code provided its virtual environment
-FROM python:3.12-slim as runtime
-
-RUN apt-get update && apt-get install -y curl
-
-WORKDIR /code
-
-ENV VIRTUAL_ENV=/code/.venv \
-    PATH="/code/.venv/bin:$PATH"
-
-COPY --from=builder ${VIRTUAL_ENV} ${VIRTUAL_ENV}
-
-COPY main.py ./
-
-HEALTHCHECK \
-    --interval=5s \
-    --timeout=1s \
-    --start-period=1s \
-    --retries=3 \
-    CMD curl http://localhost:80/healthz
-
-CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "80", "--log-level", "debug"]