feat: add docker migrator service following ItemTracker pattern

- migrations service uses mcr.microsoft.com/dotnet/sdk:10.0
- mounts source, installs dotnet-ef, retries until DB is ready
- api and worker depend on migrator completing successfully
- removed startup migration from Program.cs

Ref: IT-628

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

docker/environments/docker-compose.yml

@@ -1,4 +1,20 @@
 services:
+  migrator:
+    image: mcr.microsoft.com/dotnet/sdk:10.0
+    working_dir: /src
+    volumes:
+      - ../..:/src
+    environment:
+      - App__ConnectionString=${CONNECTION_STRING}
+    depends_on:
+      db:
+        condition: service_started
+    command:
+      - /bin/sh
+      - -c
+      - dotnet tool install --tool-path /tmp/dotnet-tools dotnet-ef --version "9.*" && until /tmp/dotnet-tools/dotnet-ef database update --project /src/HrynCo.NotificationService.DAL.EF --startup-project /src/HrynCo.NotificationService.Web; do echo "Migration failed, retrying in 3s..."; sleep 3; done
+    restart: "no"
+
   api:
     build:
       context: ../..
@@ -9,7 +25,10 @@ services:
     ports:
       - "8080:8080"
     depends_on:
-      - db
+      db:
+        condition: service_started
+      migrator:
+        condition: service_completed_successfully
 
   worker:
     build:
@@ -19,4 +38,7 @@ services:
       - DOTNET_ENVIRONMENT=Production
       - App__ConnectionString=${CONNECTION_STRING}
     depends_on:
-      - db
+      db:
+        condition: service_started
+      migrator:
+        condition: service_completed_successfully