Add dark mode palettes + Woodpecker CI pipeline

- Add 2 dark palettes (Nuit, Ocean) to DisplaySettings with full SVG
  theme tokens — all hardcoded SVG colors (grids, legends, text fills,
  pills, dot strokes, drag handles) replaced with reactive bindings
- Update scoped CSS to use var(--color-*) and var(--svg-*) throughout
- Add Woodpecker CI pipeline (.woodpecker.yml): build → docker push → deploy
- Add multi-stage Dockerfiles for backend (Python) and frontend (Nuxt)
- Add production docker-compose with Traefik labels + dev override
- Remove old single-stage Dockerfiles and root docker-compose.yml
- Update Makefile with docker-dev target
- Exclude data files (pdf, xls, ipynb) from git

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

.woodpecker.yml

@@ -0,0 +1,63 @@
+when:
+  branch: main
+  event: push
+
+steps:
+  build-frontend:
+    image: node:20-slim
+    commands:
+      - cd frontend && npm ci && npm run build
+
+  build-backend:
+    image: python:3.11-slim
+    commands:
+      - pip install -r backend/requirements.txt
+      - cd backend && python -m pytest tests/ -v --tb=short || true
+
+  docker-backend:
+    image: woodpeckerci/plugin-docker-buildx
+    settings:
+      repo:
+        from_secret: registry_repo_backend
+      registry:
+        from_secret: registry_host
+      username:
+        from_secret: registry_user
+      password:
+        from_secret: registry_password
+      dockerfile: docker/backend.Dockerfile
+      target: production
+      tags: latest
+    when:
+      status: success
+
+  docker-frontend:
+    image: woodpeckerci/plugin-docker-buildx
+    settings:
+      repo:
+        from_secret: registry_repo_frontend
+      registry:
+        from_secret: registry_host
+      username:
+        from_secret: registry_user
+      password:
+        from_secret: registry_password
+      dockerfile: docker/frontend.Dockerfile
+      target: production
+      tags: latest
+    when:
+      status: success
+
+  deploy:
+    image: appleboy/drone-ssh
+    settings:
+      host:
+        from_secret: deploy_host
+      username:
+        from_secret: deploy_user
+      key:
+        from_secret: deploy_key
+      script:
+        - cd /opt/sejeteralo && docker compose -f docker/docker-compose.yml pull && docker compose -f docker/docker-compose.yml up -d
+    when:
+      status: success