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/backend.Dockerfile

@@ -0,0 +1,38 @@
+# syntax = docker/dockerfile:1
+
+FROM python:3.11-slim AS base
+
+WORKDIR /app
+
+# Build (install dependencies)
+FROM base AS build
+
+COPY backend/requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY backend/ .
+
+# Production
+FROM base AS production
+
+ENV PYTHONUNBUFFERED=1
+
+COPY --from=build /usr/local/lib/python3.11/site-packages /usr/local/lib/python3.11/site-packages
+COPY --from=build /usr/local/bin/uvicorn /usr/local/bin/uvicorn
+COPY --from=build /usr/local/bin/alembic /usr/local/bin/alembic
+COPY --from=build /app /app
+
+HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
+  CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8000/docs')" || exit 1
+
+EXPOSE 8000
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]
+
+# Development
+FROM base AS development
+
+COPY backend/requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+WORKDIR /app
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000", "--reload"]