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

roles/postgresql/defaults/main.yml

@@ -0,0 +1,21 @@
+---
+# PostgreSQL
+postgresql_version: "17"
+postgresql_port: 5432
+postgresql_listen_addresses: "*"
+postgresql_data_dir: "/var/lib/postgresql/{{ postgresql_version }}/main"
+
+# Database configuration
+postgresql_databases:
+  - name: testdb
+    owner: testuser
+
+postgresql_users:
+  - name: testuser
+    password: "testpassword123"
+    databases: [testdb]
+    privileges: ["ALL"]
+
+# Postgres exporter user (for metrics collection)
+postgres_exporter_user: "postgres_exporter"
+postgres_exporter_password: "exporterpassword123"