✨ 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_repo/tasks/main.yml

@@ -0,0 +1,14 @@
+- name: Download GNU Taler archive key
+  ansible.builtin.get_url:
+    url: "{{ taler_config.package_repo }}taler-archive-keyring.gpg"
+    dest: /usr/share/keyrings/taler-archive-keyring.gpg
+    mode: "0644"
+    owner: root
+    group: root
+
+- name: Add GNU Taler apt repository
+  ansible.builtin.apt_repository:
+    repo: "deb [signed-by=/usr/share/keyrings/taler-archive-keyring.gpg] {{ taler_config.package_repo }} {{ taler_config.distribution }} main"
+    filename: taler
+    state: present
+  notify: Update apt cache for Taler repo