add CI/CD pipeline with blue-green deployment

GitLab CI runs pytest + ruff on master/MRs, then auto-deploys via SSH.
Blue-green strategy using Docker Compose profiles with an nginx router
on port 5000 for zero-downtime switching between slots.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitlab-ci.yml

@@ -0,0 +1,32 @@
+stages:
+  - test
+  - deploy
+
+test:
+  stage: test
+  image: python:3.12-slim
+  before_script:
+    - pip install uv
+  script:
+    - cd padelnomics && uv sync
+    - uv run pytest tests/ -x -q
+    - uv run ruff check src/ tests/
+  rules:
+    - if: $CI_COMMIT_BRANCH == "master"
+    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
+
+deploy:
+  stage: deploy
+  image: alpine:latest
+  needs: [test]
+  rules:
+    - if: $CI_COMMIT_BRANCH == "master"
+  before_script:
+    - apk add --no-cache openssh-client
+    - eval $(ssh-agent -s)
+    - echo "$SSH_PRIVATE_KEY" | tr -d '\r' | ssh-add -
+    - mkdir -p ~/.ssh
+    - chmod 700 ~/.ssh
+    - echo "$SSH_KNOWN_HOSTS" >> ~/.ssh/known_hosts
+  script:
+    - ssh "$DEPLOY_USER@$DEPLOY_HOST" "cd /opt/padelnomics && git pull origin master && ./deploy.sh"