feat(pipeline): add Meltano + dbt + Airflow ELT pipeline scaffold

Replaces the hand-rolled integrator with a production-grade ELT pipeline
using Meltano (Singer taps), dbt Core (medallion architecture), and
Apache Airflow (orchestration). Adds Typesense for search and PostGIS
for geospatial queries.

- 6 custom Singer taps (GIAS, EES, Ofsted, Parent View, FBIT, IDACI)
- dbt project: 12 staging, 5 intermediate, 12 mart models
- 3 Airflow DAGs (daily/monthly/annual schedules)
- Typesense sync + batch geocoding scripts
- docker-compose: add Airflow, Typesense; upgrade to PostGIS
- Portainer stack definition matching live deployment topology

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pipeline/Dockerfile

@@ -0,0 +1,37 @@
+FROM python:3.12-slim
+
+WORKDIR /opt/pipeline
+
+# System dependencies
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    gcc \
+    libpq-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+# Python dependencies
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+# Install custom Singer taps
+COPY plugins/ plugins/
+RUN pip install --no-cache-dir \
+    ./plugins/extractors/tap-uk-gias \
+    ./plugins/extractors/tap-uk-ees \
+    ./plugins/extractors/tap-uk-ofsted \
+    ./plugins/extractors/tap-uk-parent-view \
+    ./plugins/extractors/tap-uk-fbit \
+    ./plugins/extractors/tap-uk-idaci
+
+# Copy pipeline code
+COPY meltano.yml .
+COPY transform/ transform/
+COPY scripts/ scripts/
+COPY dags/ dags/
+
+# dbt deps
+RUN cd transform && dbt deps --profiles-dir . 2>/dev/null || true
+
+ENV AIRFLOW_HOME=/opt/airflow
+ENV PYTHONPATH=/opt/pipeline
+
+CMD ["airflow", "webserver"]