docs: [#26] add 12-factor deployment process overview

- Add comprehensive 4-step deployment process section to README.md
- Enhance cloud deployment guide with detailed workflow explanation
- Add ADR reference table to copilot instructions for contributor guidance
- Clarify separation between infrastructure provisioning and application deployment
- Document Build/Release/Run stages alignment with twelve-factor methodology

Author: josecelano

.github/copilot-instructions.md

@@ -182,6 +182,19 @@ torrust-tracker-demo/
 - **Cross-cutting**: Project-wide documentation and ADRs
 - **Architecture Decisions**: Documented design choices and rationale
 
+#### Architecture Decision Records (ADRs)
+
+Key design decisions are documented in `docs/adr/`. Contributors should review relevant ADRs when working on related features:
+
+| ADR | Title | Description |
+|-----|-------|-------------|
+| [ADR-001](../docs/adr/001-makefile-location.md) | Makefile Location | Why the main Makefile is at repository root |
+| [ADR-002](../docs/adr/002-docker-for-all-services.md) | Docker for All Services | Why we use Docker for all services including UDP tracker |
+| [ADR-003](../docs/adr/003-use-mysql-over-mariadb.md) | Use MySQL Over MariaDB | Database backend selection rationale |
+| [ADR-004](../docs/adr/004-configuration-approach-files-vs-environment-variables.md) | Configuration Approach | Files vs environment variables for configuration |
+| [ADR-005](../docs/adr/005-sudo-cache-management-for-infrastructure-operations.md) | Sudo Cache Management | Managing sudo credentials during infrastructure operations |
+| [ADR-006](../docs/adr/006-ssl-certificate-generation-strategy.md) | SSL Certificate Generation Strategy | Approach for SSL certificate management |
+
 ## 🛠️ Development Workflow
 
 ### Quick Start for Contributors

README.md

@@ -90,6 +90,51 @@ clear separation between infrastructure provisioning and application deployment:
 - **Environment-based Configuration**: Template system with `local.env.tpl` and `production.env.tpl`
 - **Build/Release/Run Stages**: Proper separation of configuration processing, deployment, and execution
 
+## 🚀 Deployment Process Overview
+
+This project follows a **four-step deployment process** based on twelve-factor app principles:
+
+### 1. **Configure Environment Variables**
+
+Customize deployment settings using environment-specific templates:
+
+- `infrastructure/config/environments/local.env.tpl` → `local.env`
+- `infrastructure/config/environments/production.env.tpl` → `production.env`
+- Contains ALL deployment configuration (infrastructure, SSL, backups, application secrets)
+
+### 2. **Provision Infrastructure**
+
+Create and configure the target environment:
+
+- **VM Creation**: Deploy virtual machine with specified resources
+- **System Setup**: cloud-init installs dependencies, configures firewall, sets up users
+- **Platform Preparation**: Ready environment for application deployment
+
+### 3. **Deploy Application** (Build + Release + Run Stages)
+
+Deploy the application stack following twelve-factor principles:
+
+- **Build**: Prepare application artifacts and configuration files
+- **Release**: Generate SSL certificates, create Docker environment files, copy configs
+- **Run**: Start Docker Compose stack (tracker, MySQL, Nginx, Grafana, Prometheus)
+
+### 4. **Validation**
+
+Verify deployment health and functionality:
+
+- Service health checks (HTTP/UDP endpoints)
+- Database connectivity validation
+- Monitoring dashboard accessibility
+- End-to-end smoke testing
+
+### Quick Commands
+
+```bash
+make infra-apply ENVIRONMENT=local      # Steps 1-2: Configure + Provision
+make app-deploy ENVIRONMENT=local       # Step 3: Deploy Application
+make app-health-check ENVIRONMENT=local # Step 4: Validation
+```
+
 ## Demo Tracker
 
 - **HTTP Tracker**: <https://tracker.torrust-demo.com/announce>

docs/guides/cloud-deployment-guide.md

@@ -12,6 +12,53 @@ and testing. Hetzner Cloud support is planned as the next implementation target.
 The process combines Infrastructure as Code with application deployment automation to
 provide a streamlined deployment experience, following twelve-factor app methodology.
 
+## Deployment Process
+
+This project implements a **four-step deployment workflow** aligned with twelve-factor app principles:
+
+### Step 1: Configure Environment Variables
+
+Create environment-specific configuration from templates:
+
+- **Local Development**: `infrastructure/config/environments/local.env.tpl` → `local.env`
+- **Production**: `infrastructure/config/environments/production.env.tpl` → `production.env`
+
+The environment file contains **all deployment configuration**, including:
+
+- Infrastructure settings (VM specs, network configuration)
+- Application secrets (database passwords, API tokens)
+- SSL certificate configuration (domains, email for Let's Encrypt)
+- Backup and monitoring settings
+
+### Step 2: Provision Infrastructure
+
+Deploy and configure the target environment:
+
+- **VM Creation**: Deploy virtual machine with specified resources
+- **System Dependencies**: cloud-init installs Docker, configures firewall, creates users
+- **Network Setup**: Configure firewall rules, SSH access, system security
+- **Platform Readiness**: Environment prepared for application deployment
+
+### Step 3: Deploy Application (Build + Release + Run)
+
+Deploy the application stack following twelve-factor methodology:
+
+- **Build Stage**: Prepare application artifacts and configuration templates
+- **Release Stage**:
+  - Generate SSL certificates (Let's Encrypt or self-signed)
+  - Create Docker environment files from templates
+  - Copy application configurations to target VM
+- **Run Stage**: Start Docker Compose stack (Torrust Tracker, MySQL, Nginx, Grafana, Prometheus)
+
+### Step 4: Validation
+
+Verify deployment health and functionality:
+
+- **Service Health**: HTTP/UDP endpoint availability checks
+- **Database Connectivity**: MySQL connection and schema validation
+- **Monitoring Access**: Grafana dashboard accessibility
+- **End-to-end Testing**: Tracker announce/scrape functionality
+
 ## Prerequisites
 
 ### Local Requirements