docs: add docker.md — full Docker distribution architecture plan

Covers all six services (jarvisChat, SearXNG, Qdrant, RabbitMQ,
llama-server, Ollama) with images, ports, volumes, healthchecks,
env mapping, secrets management, setup wizard spec, and back-out
procedure. Includes pre-v1.0 gate checklist and open decisions.

Also add .env, secrets/, searxng/ to .gitignore (these are
generated by setup.sh and contain secrets).

.gitignore

@@ -6,3 +6,6 @@ venv/
 readme.md-
 *.bak
 hardware_state.json
+.env
+secrets/
+searxng/