fix(kestra-init): use alpine+curl instead of kestra image to avoid 413

kestra/kestra:latest is ~500MB; the registry rejects the push.
The init container only needs to POST flow YAMLs to the Kestra REST API
(/api/v1/flows/import), which curl handles fine from a tiny alpine base.

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

docker-compose.yml

@@ -114,24 +114,8 @@ services:
   kestra-init:
     image: privaterepo.sitaru.org/tudor/school_compare-kestra-init:latest
     container_name: schoolcompare_kestra_init
-    command: flow namespace update schoolcompare.data /flows --no-delete
     environment:
-      KESTRA_CONFIGURATION: |
-        datasources:
-          postgres:
-            url: jdbc:postgresql://db:5432/kestra
-            driverClassName: org.postgresql.Driver
-            username: schoolcompare
-            password: schoolcompare
-        kestra:
-          repository:
-            type: postgres
-          queue:
-            type: postgres
-          storage:
-            type: local
-            local:
-              base-path: /tmp/kestra-init-storage
+      KESTRA_URL: http://kestra:8080
     depends_on:
       kestra:
         condition: service_healthy