svc-db-postgres: add retry mechanism to all PostgreSQL tasks and fix condition handling

- Added register, until, retries, and delay to all PostgreSQL-related tasks
  in 02_init.yml to handle transient 'tuple concurrently updated' and similar errors.
- Changed 'when: "{{ postgres_init }}"' to 'when: postgres_init | bool' in main.yml
  for correct boolean evaluation.
- Switched 'role' to 'roles' in postgresql_privs tasks for forward compatibility.
- Added postgres_retry_retries and postgres_retry_delay defaults in vars/main.yml
  to centralize retry configuration.

  https://chatgpt.com/share/689b2360-a8a4-800f-9acb-6d88d6aa5cb7

roles/svc-db-postgres/tasks/main.yml

@@ -10,4 +10,4 @@
 
 - name: "Initialize database for '{{ database_name }}'"
   include_tasks: 02_init.yml
-  when: "{{ postgres_init }}"
+  when: postgres_init | bool