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>

docker/frontend.Dockerfile

@@ -0,0 +1,36 @@
+# syntax = docker/dockerfile:1
+
+ARG NODE_VERSION=20-slim
+
+FROM node:${NODE_VERSION} AS base
+
+WORKDIR /src
+
+# Build
+FROM base AS build
+
+COPY frontend/package.json frontend/package-lock.json ./
+RUN npm ci
+
+COPY frontend/ .
+RUN npm run build
+
+# Production
+FROM base AS production
+
+ENV PORT=3000
+ENV NODE_ENV=production
+
+COPY --from=build /src/.output /src/.output
+
+HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
+  CMD curl -f http://localhost:${PORT}/ || exit 1
+
+EXPOSE $PORT
+CMD [ "node", ".output/server/index.mjs" ]
+
+# Development
+FROM base AS development
+
+WORKDIR /app
+ENTRYPOINT [ "npm", "run", "dev" ]