Phase 1 : pipeline d'ingestion Sentinel-2

- SentinelHubClient : auth OAuth2, Catalog API (cloud coverage),
  Process API avec evalscript AFAI binaire (UINT8, cloud-side)
- IngestionService : orchestration complète — job tracking,
  rejet nuages, téléchargement GeoTIFF, polygonize GDAL,
  simplification PostGIS, persistance SargassumObservation
- IngestSentinelCommand : 5 zones Antilles configurées,
  options --date et --zone, appelable via cron docker exec
- Dockerfile : ajout gdal-bin + python3-gdal
- Correction entity : paramètre immutable retiré de #[ORM\Column]

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

backend/config/reference.php

@@ -472,7 +472,7 @@ use Symfony\Component\Config\Loader\ParamConfigurator as Param;
  *     },
  *     disallow_search_engine_index?: bool|Param, // Enabled by default when debug is enabled. // Default: true
  *     http_client?: bool|array{ // HTTP Client configuration
- *         enabled?: bool|Param, // Default: false
+ *         enabled?: bool|Param, // Default: true
  *         max_host_connections?: int|Param, // The maximum number of connections to a single host.
  *         default_options?: array{
  *             headers?: array<string, mixed>,