chore(compose): replace all build: directives with registry images

All four custom services now pull pre-built images from the registry
instead of building on the host. Also switches the integrator data
volume to a named volume (supplementary_data) since bind mounts to
./data won't exist on the Portainer host.

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

docker-compose.yml

@@ -25,9 +25,7 @@ services:
 
   # FastAPI Backend
   backend:
-    build:
+    image: privaterepo.sitaru.org/tudor/school_compare-backend:latest
-      context: .
-      dockerfile: Dockerfile
     container_name: schoolcompare_backend
     ports:
       - "8000:80"
@@ -52,17 +50,12 @@ services:
 
   # Next.js Frontend
   nextjs:
-    build:
+    image: privaterepo.sitaru.org/tudor/school_compare-frontend:latest
-      context: ./nextjs-app
-      dockerfile: Dockerfile
-      args:
-        FASTAPI_URL: http://backend:80/api
     container_name: schoolcompare_nextjs
     ports:
       - "3000:3000"
     environment:
       NODE_ENV: production
-      # Next.js can access backend via internal network
       NEXT_PUBLIC_API_URL: http://localhost:8000/api
       FASTAPI_URL: http://backend:80/api
     depends_on:
@@ -121,6 +114,7 @@ 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:
@@ -138,8 +132,6 @@ services:
             type: local
             local:
               base-path: /tmp/kestra-init-storage
-    command: >
-      flow namespace update schoolcompare.data /flows --no-delete
     depends_on:
       kestra:
         condition: service_healthy
@@ -149,9 +141,7 @@ services:
 
   # Data integrator — Python microservice called by Kestra
   integrator:
-    build:
+    image: privaterepo.sitaru.org/tudor/school_compare-integrator:latest
-      context: ./integrator
-      dockerfile: Dockerfile
     container_name: schoolcompare_integrator
     ports:
       - "8001:8001"
@@ -162,7 +152,7 @@ services:
       ADMIN_API_KEY: ${ADMIN_API_KEY:-changeme}
       PYTHONUNBUFFERED: 1
     volumes:
-      - ./data:/data
+      - supplementary_data:/data
     depends_on:
       db:
         condition: service_healthy
@@ -183,3 +173,4 @@ networks:
 volumes:
   postgres_data:
   kestra_storage:
+  supplementary_data: