✨ 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/env_config/tasks/main.yml

@@ -0,0 +1,66 @@
+---
+- name: Determine project root
+  set_fact:
+    project_root: "{{ (playbook_dir | realpath) | dirname }}"
+
+- name: Set default .env path
+  set_fact:
+    env_file_resolved: "{{ lookup('ansible.builtin.env', 'GNUTALER_ENV_FILE') }}"
+
+- name: Override .env path with project default when not provided
+  set_fact:
+    env_file_resolved: "{{ project_root + '/.env' }}"
+  when: env_file_resolved | default('') | length == 0
+
+- name: Check if .env file exists
+  ansible.builtin.stat:
+    path: "{{ env_file_resolved }}"
+  register: env_file_stat
+
+- name: Load .env overrides when present
+  set_fact:
+    env_overrides: "{{ lookup('community.general.read_env', env_file_resolved) }}"
+  when: env_file_stat.stat.exists
+
+- name: Warn when .env file is missing
+  ansible.builtin.debug:
+    msg: >-
+      .env file not found at {{ env_file_resolved }}.
+      Using defaults from group_vars/all.yml. Create one from .env-example.
+  when: not env_file_stat.stat.exists
+
+- name: Merge defaults with .env overrides
+  set_fact:
+    taler_env: "{{ taler_defaults | combine(env_overrides | default({}), recursive=True) }}"
+
+- name: Build structured variables for play consumption
+  set_fact:
+    taler_config:
+      domain: "{{ taler_env.TALER_DOMAIN }}"
+      admin_email: "{{ taler_env.TALER_ADMIN_EMAIL }}"
+      acme_contact: "{{ taler_env.LETSENCRYPT_CONTACT }}"
+      package_repo: "{{ taler_env.TALER_PACKAGE_REPO }}"
+      distribution: "{{ taler_env.TALER_DISTRIBUTION }}"
+      currency: "{{ taler_env.TALER_CURRENCY }}"
+      exchange_host: "{{ taler_env.TALER_EXCHANGE_HOST }}"
+      merchant_host: "{{ taler_env.TALER_MERCHANT_HOST }}"
+      pay_host: "{{ taler_env.TALER_PAY_HOST }}"
+      wordpress_host: "{{ taler_env.WORDPRESS_HOST }}"
+      exchange_master_key: "{{ taler_env.TALER_MASTER_PUBLIC_KEY }}"
+      db:
+        host: "{{ taler_env.TALER_DB_HOST }}"
+        port: "{{ taler_env.TALER_DB_PORT | int }}"
+        admin_user: "{{ taler_env.TALER_DB_ADMIN_USER }}"
+        admin_password: "{{ taler_env.TALER_DB_ADMIN_PASSWORD }}"
+        exchange:
+          name: "{{ taler_env.TALER_EXCHANGE_DB }}"
+          user: "{{ taler_env.TALER_EXCHANGE_DB_USER }}"
+          password: "{{ taler_env.TALER_EXCHANGE_DB_PASSWORD }}"
+        merchant:
+          name: "{{ taler_env.TALER_MERCHANT_DB }}"
+          user: "{{ taler_env.TALER_MERCHANT_DB_USER }}"
+          password: "{{ taler_env.TALER_MERCHANT_DB_PASSWORD }}"
+      wordpress_db:
+        name: "{{ taler_env.WORDPRESS_DB_NAME }}"
+        user: "{{ taler_env.WORDPRESS_DB_USER }}"
+        password: "{{ taler_env.WORDPRESS_DB_PASSWORD }}"