Update CI for docker

.gitlab-ci.yml

-image: python:3.9  # Use a Python Docker image
+image: docker:20.10.16  # Define the Docker image
 
 stages:  # Define stages in the pipeline
   - prepare
@@ -6,8 +6,9 @@ stages:  # Define stages in the pipeline
   - deploy
 
 prepare:
-  image: docker:20.10.16
-  stage: build
+  stage: prepare
+  tags:
+    - docker
   services:
     - docker:20.10.16-dind
   before_script:
@@ -22,20 +23,34 @@ prepare:
 # Job to build documentation
 build-docs:
   stage: build
+  dependencies:
+    - prepare
+  image:
+    name: $CI_REGISTRY_IMAGE:latest
+    entrypoint: [""]
+  tags:
+    - docker
   script:
     - sphinx-build docs/source docs/build  # Build the documentation
   artifacts:
     paths:
       - docs/build  # Save the build output for later stages
     expire_in: 12 month  # Optional: Set how long to keep the artifacts (default: 30 days)
-
+  
 # Job to deploy documentation to GitLab Pages
 pages:
   stage: deploy
+  dependencies:
+  - prepare
+  image:
+    name: $CI_REGISTRY_IMAGE:latest
+    entrypoint: [""]
+  tags:
+    - docker
   script:
     - mv docs/build public  # Move the build output to the "public" directory
   artifacts:
     paths:
       - public  # Files in the "public" folder will be deployed to GitLab Pages
   only:
-    - main  # Only deploy if the changes are in the default branch
+    - main  # Only deploy if the changes are in the default branch
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