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>

backend/Dockerfile

@@ -1,12 +0,0 @@
-FROM python:3.11-slim
-
-WORKDIR /app
-
-COPY requirements.txt .
-RUN pip install --no-cache-dir -r requirements.txt
-
-COPY . .
-
-EXPOSE 8000
-
-CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]