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>

Makefile

@@ -1,6 +1,6 @@
-.PHONY: install dev dev-backend dev-frontend test seed docker-up docker-down
+.PHONY: install dev dev-backend dev-frontend test seed docker-up docker-down docker-dev
 
-# ── Development ──
+# ── Development (local) ──
 
 install:
 	cd backend && python3 -m venv venv && . venv/bin/activate && pip install -r requirements.txt
@@ -20,10 +20,15 @@ test:
 seed:
 	cd backend && . venv/bin/activate && python seed.py
 
-# ── Docker ──
+# ── Docker (production) ──
 
 docker-up:
-	docker compose up --build -d
+	docker compose -f docker/docker-compose.yml up --build -d
 
 docker-down:
-	docker compose down
+	docker compose -f docker/docker-compose.yml down
+
+# ── Docker (dev) ──
+
+docker-dev:
+	docker compose -f docker/docker-compose.yml -f docker/docker-compose.dev.yml up --build