Add deployment pipeline, Dockerfile, Nomad spec and tests

- Dockerfile: python:3.12-slim + gunicorn, dynamic port, BUILD_VERSION args
- punktfri.nomad: Traefik routing for punktfri.i80.dk, host volume for SQLite
- .gitea/workflows/deploy.yml: build/push to Harbor, deploy to Nomad
- Makefile: install/run/test/build targets
- tests/test_app.py: 9 pytest tests covering all routes and validation
- requirements.txt: add gunicorn
- requirements-dev.txt: pytest
- app.py: health endpoint returns version/commit info

Dockerfile

@@ -0,0 +1,29 @@
+FROM python:3.12-slim
+
+ARG BUILD_VERSION=dev
+ARG GIT_COMMIT=unknown
+ARG BUILD_TIME=unknown
+
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    FLASK_APP=app.py \
+    BUILD_VERSION=${BUILD_VERSION} \
+    GIT_COMMIT=${GIT_COMMIT} \
+    BUILD_TIME=${BUILD_TIME} \
+    PORT=5000 \
+    HOST=0.0.0.0 \
+    DATABASE=/app/instance/punktfri.db \
+    LOG_FILE=/app/instance/signups.log
+
+WORKDIR /app
+
+COPY requirements.txt ./
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY . .
+
+RUN mkdir -p /app/instance
+
+EXPOSE 5000
+
+CMD ["sh", "-c", "gunicorn --bind ${HOST}:${PORT} --workers 2 --timeout 60 app:app"]