Add production compose stack and env template

deploy/compose.yaml defines project "mealquest": the mealquest service built
from the root Dockerfile, running as 10001:10001, configured from deploy/.env
and Docker secrets in deploy/secrets/, with the mealquest-data volume at
/data, published on ${MEALQUEST_BIND_ADDRESS}:8090, a /health healthcheck and
restart unless-stopped, on the private mealquest network.

deploy/.env.example documents every MEALQUEST_* variable: the ones operators
set, the ones fixed by compose.yaml, and the planned ones not yet read.
.gitignore keeps deploy/.env and deploy/secrets/ out while tracking the
example.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -3,6 +3,8 @@ design/.DS_Store
 
 # Secrets and local environment
 .env*
+!deploy/.env.example
+deploy/.env
 deploy/secrets/
 
 # Build artifacts and dependencies