refactor(infra) : reorganize docker config into infra/dev and infra/prod

Align project structure with Lesstime: move docker/ to infra/dev/ and
deploy/ to infra/prod/. Update all references in docker-compose,
makefile, CI workflow, Dockerfile, .gitignore and .dockerignore.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.dockerignore

@@ -2,10 +2,10 @@
 .gitea
 .env.local
 .env.test
-docker/
-deploy/docker/docker-compose.prod.yml
-deploy/docker/deploy.sh
-deploy/docker/.env.example
+infra/dev/
+infra/prod/docker-compose.yml
+infra/prod/deploy.sh
+infra/prod/.env.example
 frontend/node_modules
 frontend/.nuxt
 frontend/.output