feat: add PostgreSQL infrastructure for App2

- Add PostgreSQL role for installing and configuring PostgreSQL 17
- Add postgres_exporter role for PostgreSQL metrics collection
- Add deploy-postgres-app2.yml playbook for deployment
- Configure test database 'testdb' with user 'testuser'
- Set up postgres_exporter user for monitoring
- Include firewall configuration for PostgreSQL (5432) and postgres_exporter (9187)
- Follow existing role structure pattern from node_exporter

playbooks/deploy-postgres-app2.yml

@@ -0,0 +1,12 @@
+---
+- name: Deploy PostgreSQL and Postgres Exporter on App2
+  hosts: 192.168.0.111
+  become: yes
+  gather_facts: yes
+
+  roles:
+    - role: postgresql
+      tags: postgresql
+
+    - role: postgres_exporter
+      tags: postgres_exporter