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/run.yml

@@ -88,3 +88,8 @@
       tags: docker
     - role: nvidia_gpu
       tags: gpu
+    # renders services/phy-srv-gpu01/*/compose.yml into ~/docker/compose.yaml.
+    # It only WRITES the file — starting the stack stays a deliberate manual
+    # step (see ansible/services/phy-srv-gpu01/README.md).
+    - role: ironicbadger.docker_compose_generator
+      tags: compose