Deploy: MariaDB from Gitea registry to fix amd64 manifest error

- Use image 10.0.10.205:3000/bert.hausmans/mariadb:11 in compose
- Add deploy/mariadb/Dockerfile (FROM mariadb:11, platform amd64)
- Add scripts/push-mariadb-to-registry.sh to build and push amd64 image once
- Update README with one-time push step and troubleshooting

Co-authored-by: Cursor <cursoragent@cursor.com>

deploy/docker-compose.yml

@@ -65,17 +65,18 @@ services:
     networks:
       - event-uploader
 
+  # MariaDB from Gitea (use scripts/push-mariadb-to-registry.sh once if missing)
   mysql:
-    image: docker.io/library/mysql:8.0
+    image: 10.0.10.205:3000/bert.hausmans/mariadb:11
     ports:
       - "3004:3306"
     environment:
-      MYSQL_ROOT_PASSWORD: ${DB_PASSWORD}
-      MYSQL_DATABASE: ${DB_DATABASE:-event_uploader}
+      MARIADB_ROOT_PASSWORD: ${DB_PASSWORD}
+      MARIADB_DATABASE: ${DB_DATABASE:-event_uploader}
     volumes:
       - event_uploader_mysql_data:/var/lib/mysql
     healthcheck:
-      test: ["CMD", "mysqladmin", "ping", "-h", "localhost", "-p${DB_PASSWORD}"]
+      test: ["CMD", "mariadb-admin", "ping", "-h", "localhost", "-p${DB_PASSWORD}"]
       interval: 5s
       timeout: 5s
       retries: 10