Improve docker build

- add .dockerignore
- add entrypoint.sh to ensure proper permissions in Docker volumes
- add TZ variable for consistent Celery timestamps

.dockerignore

@@ -0,0 +1,18 @@
+**/*.pyc
+**/.*.swp
+**/.coverage
+**/__pycache__
+.dockerignore
+.env
+.envrc
+.git
+.gitignore
+.idea
+.isort.cfg
+.vagrant
+Dockerfile
+Vagrantfile
+docker-compose.yml
+docs
+media
+static