Improve oracle-db-postinstall role robustness

- Enhance systemd service template with proper User/Group/Environment settings
- Use variables in cron cleaner script instead of hardcoded paths
- Add comprehensive path validations before operations
- Create validations.yml for prerequisite checks
- Improve service dependencies and startup order

roles/oracle-db-postinstall/tasks/main.yml

@@ -10,11 +10,8 @@
     msg: "Prérequis non satisfaits : RAM >= 2GB"
   tags: prerequisites
 
-- name: Vérifier que Oracle est installé
-  ansible.builtin.stat:
-    path: "{{ oracle_home }}/bin/sqlplus"
-  register: oracle_installed
-  failed_when: not oracle_installed.stat.exists
+- name: Inclure les validations des chemins et fichiers
+  ansible.builtin.include_tasks: validations.yml
   tags: prerequisites
 
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