Phase 0 : entités, migrations, API Platform, PostGIS

- API Platform + Doctrine ORM + jsor/doctrine-postgis installés
- 6 entités Symfony (SargassumObservation, SargassumForecast,
  DataIngestionJob, CoastalPoint, ImpactScore, UserFeedback)
- Migration initiale manuelle avec CREATE EXTENSION postgis,
  toutes les tables, index GIST et BTREE
- doctrine.yaml configuré pour PostgreSQL 16 + types PostGIS
- Roadmap Phase 0 complète

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

backend/compose.yaml

@@ -0,0 +1,25 @@
+
+services:
+###> doctrine/doctrine-bundle ###
+  database:
+    image: postgres:${POSTGRES_VERSION:-16}-alpine
+    environment:
+      POSTGRES_DB: ${POSTGRES_DB:-app}
+      # You should definitely change the password in production
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-!ChangeMe!}
+      POSTGRES_USER: ${POSTGRES_USER:-app}
+    healthcheck:
+      test: ["CMD", "pg_isready", "-d", "${POSTGRES_DB:-app}", "-U", "${POSTGRES_USER:-app}"]
+      timeout: 5s
+      retries: 5
+      start_period: 60s
+    volumes:
+      - database_data:/var/lib/postgresql/data:rw
+      # You may use a bind-mounted host directory instead, so that it is harder to accidentally remove the volume and lose all your data!
+      # - ./docker/db/data:/var/lib/postgresql/data:rw
+###< doctrine/doctrine-bundle ###
+
+volumes:
+###> doctrine/doctrine-bundle ###
+  database_data:
+###< doctrine/doctrine-bundle ###