Add LLM compose stack for phy-srv-gpu01 (not deployed yet)

Follows the homelab pattern: ironicbadger.docker_compose_generator v2
renders services/<host>/NN-<stack>/compose.yml templates into
~/docker/compose.yaml on the host.

- 01-vllm: chat model, fixed --gpu-memory-utilization
- 02-embeddings: second vLLM instance (--task embed) rather than a
  separate toolchain, so SM120 support only has to be solved once
- 03-openwebui: Open WebUI + pgvector (not chroma — corpus size)
- 99-network: shared bridge; leading comment keeps networks: top-level
- pin docker_compose_generator to 2.0.1 — galaxy tags mix v1/v2 formats
- group_vars: stack config incl. LDAP placeholders still to be filled

The role only writes the compose file; starting the stack stays manual.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ansible/services/phy-srv-gpu01/99-network/compose.yml

@@ -0,0 +1,7 @@
+# network definition (leading comment required: the compose generator
+# indents the first line of each fragment; networks: must stay top-level)
+networks:
+  llmnet:
+    driver: bridge
+    driver_opts:
+      com.docker.network.bridge.name: br-llm