✨ feat(infrastructure): introduce ansible deployment for taler services

- add ansible playbooks and roles for deploying taler exchange and merchant
- configure PostgreSQL, GNU Taler repositories, and services

🔧 chore(config): provide example env and gitignore for sensitive files

- create .env-example with placeholders for sensitive info
- add .gitignore entries for .env and common editor files

roles/taler_exchange/tasks/main.yml

@@ -0,0 +1,63 @@
+- name: Ensure master public key is provided
+  ansible.builtin.assert:
+    that:
+      - taler_config.exchange_master_key is defined
+      - taler_config.exchange_master_key | length > 0
+    fail_msg: "Provide TALER_MASTER_PUBLIC_KEY in .env before running exchange deployment."
+
+- name: Install GNU Taler exchange packages
+  ansible.builtin.apt:
+    name:
+      - taler-exchange
+      - taler-exchange-httpd
+      - taler-exchange-aggregator
+      - taler-exchange-closer
+      - taler-exchange-transfer
+      - taler-exchange-wirewatch
+    state: present
+
+- name: Ensure exchange runtime directories exist
+  ansible.builtin.file:
+    path: "{{ item }}"
+    state: directory
+    owner: taler-exchange-httpd
+    group: taler-exchange-httpd
+    mode: "0750"
+  loop:
+    - /var/lib/taler/exchange
+    - /etc/taler/conf.d
+
+- name: Deploy exchange configuration
+  ansible.builtin.template:
+    src: exchange.conf.j2
+    dest: /etc/taler/conf.d/exchange.conf
+    owner: root
+    group: root
+    mode: "0640"
+  notify:
+    - Restart taler-exchange-httpd
+    - Restart taler-exchange-aggregator
+    - Restart taler-exchange-closer
+    - Restart taler-exchange-transfer
+    - Restart taler-exchange-wirewatch
+
+- name: Run taler-exchange-dbinit
+  ansible.builtin.command:
+    cmd: taler-exchange-dbinit -c /etc/taler/conf.d/exchange.conf
+  register: dbinit_result
+  changed_when: "'already initialized' not in dbinit_result.stdout"
+  failed_when: dbinit_result.rc not in [0]
+  become: true
+  become_user: taler-exchange-httpd
+
+- name: Validate exchange configuration
+  ansible.builtin.command:
+    cmd: taler-config -c /etc/taler/conf.d/exchange.conf -s exchange -o CURRENCY
+  register: exchange_config_validation
+  changed_when: false
+
+- name: Assert exchange currency matches expected
+  ansible.builtin.assert:
+    that:
+      - exchange_config_validation.stdout.strip() == taler_config.currency
+    fail_msg: "Exchange currency does not match expected value {{ taler_config.currency }}. Check configuration."