feat: add Dockerfile and .dockerignore, refactor backend to use DATA_DIR for database and uploads

Now able to use docker image

.dockerignore

@@ -0,0 +1,10 @@
+node_modules
+frontend/node_modules
+backend/node_modules
+frontend/dist
+backend/dist
+backend/db.sqlite
+backend/uploads
+*.log
+.DS_Store
+.env