docs: rewrite README with structured overview and quick start guide

Replaces the minimal project description with a comprehensive README
including a component overview table, quick start instructions, common
Ansible operations, and links to detailed documentation. Aligns with
Red Panda Approval™ standards.

ansible/smtp4dev/deploy.yml

@@ -0,0 +1,56 @@
+---
+- name: Deploy smtp4dev with Docker Compose
+  hosts: ubuntu
+  become: true
+  vars:
+    required_service: smtp4dev
+  tasks:
+  - name: Check if host has smtp4dev service
+    ansible.builtin.set_fact:
+      has_smtp4dev_service: "{{required_service in services}}"
+
+  - name: Skip hosts without smtp4dev service
+    ansible.builtin.meta: end_host
+    when: not has_smtp4dev_service
+
+  - name: Create smtp4dev group
+    ansible.builtin.group:
+      name: "{{smtp4dev_group}}"
+
+  - name: Create smtp4dev user
+    ansible.builtin.user:
+      name: "{{smtp4dev_user}}"
+      comment: "smtp4dev"
+      group: "{{smtp4dev_group}}"
+      system: true
+
+  - name: Add group smtp4dev to user ponos
+    ansible.builtin.user:
+      name: ponos
+      groups: "{{smtp4dev_group}}"
+      append: true
+
+  - name: Create smtp4dev directory
+    ansible.builtin.file:
+      path: "{{smtp4dev_directory}}"
+      owner: "{{smtp4dev_user}}"
+      group: "{{smtp4dev_group}}"
+      state: directory
+      mode: '750'
+
+  - name: Template docker-compose file
+    ansible.builtin.template:
+      src: docker-compose.yml.j2
+      dest: "{{smtp4dev_directory}}/docker-compose.yml"
+      owner: "{{smtp4dev_user}}"
+      group: "{{smtp4dev_group}}"
+      mode: '550'
+
+  - name: Reset SSH connection to apply group changes
+    meta: reset_connection
+
+  - name: Start smtp4dev service
+    community.docker.docker_compose_v2:
+      project_src: "{{smtp4dev_directory}}"
+      state: present
+      pull: always