web-app-openproject: upgrade to OpenProject 15

- bumped image version from 14 to 15
- removed dedicated migration task (now handled by upstream entrypoints)
- renamed tasks for cleaner numbering:
  * 02_settings.yml → 01_settings.yml
  * 03_ldap.yml → 02_ldap.yml
  * 04_admin.yml → 03_admin.yml

Ref: https://chatgpt.com/share/68d57770-2430-800f-ae53-e7eda6993a8d

roles/web-app-openproject/tasks/01_settings.yml

@@ -0,0 +1,10 @@
+- name: Set settings in OpenProject
+  shell: >
+    docker compose exec {{ OPENPROJECT_WEB_SERVICE }} bash -c "cd /app &&
+    RAILS_ENV={{ ENVIRONMENT | lower }} bundle exec rails runner \"Setting[:{{ item.key }}] = '{{ item.value }}'\""
+  args:
+    chdir: "{{ docker_compose.directories.instance }}"
+  loop:   "{{ OPENPROJECT_RAILS_SETTINGS | dict2items }}"
+  async:  "{{ ASYNC_TIME if ASYNC_ENABLED | bool else omit }}"
+  poll:   "{{ ASYNC_POLL if ASYNC_ENABLED | bool else omit }}"
+  no_log: "{{ MASK_CREDENTIALS_IN_LOGS | bool }}"