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/transform/models/marts/dim_school.sql

@@ -0,0 +1,40 @@
+-- Mart: Canonical school dimension — one row per active URN
+
+with schools as (
+    select * from {{ ref('stg_gias_establishments') }}
+),
+
+latest_ofsted as (
+    select * from {{ ref('int_ofsted_latest') }}
+)
+
+select
+    s.urn,
+    s.local_authority_code * 1000 + s.establishment_number as laestab,
+    s.school_name,
+    s.phase,
+    s.school_type,
+    s.academy_trust_name,
+    s.academy_trust_uid,
+    s.religious_character,
+    s.gender,
+    s.statutory_low_age || '-' || s.statutory_high_age as age_range,
+    s.capacity,
+    s.total_pupils,
+    concat_ws(' ', s.head_title, s.head_first_name, s.head_last_name) as headteacher_name,
+    s.website,
+    s.telephone,
+    s.open_date,
+    s.close_date,
+    s.status,
+    s.nursery_provision,
+    s.admissions_policy,
+
+    -- Latest Ofsted
+    o.overall_effectiveness as ofsted_grade,
+    o.inspection_date as ofsted_date,
+    o.framework as ofsted_framework
+
+from schools s
+left join latest_ofsted o on s.urn = o.urn
+where s.status = 'Open'