Fix PM2 cluster mode environment variable loading (#379)

Problem:
- When running with `pm2 start` in cluster mode, Node.js 22's --env-file flag was not being passed
- This caused all process.env variables to be undefined, breaking database connections and app configuration
- The issue only occurred in PM2 deployments; npm start worked correctly

Solution:
- Created ecosystem.config.js to configure PM2 with proper node_args
- Added --env-file=config.env --env-file=.env flags to node_args
- Updated CI/CD workflows (cd_dev.yaml and cd_prod.yaml) to use ecosystem config
- Configured separate development and production environments

Changes:
- NEW: ecosystem.config.js - PM2 configuration with cluster mode and env loading
- UPDATED: .github/workflows/cd_dev.yaml - Use ecosystem config for development deployment
- UPDATED: .github/workflows/cd_prod.yaml - Use ecosystem config for production deployment

Testing:
- Local: pm2 start ecosystem.config.js --env development
- Verify env variables load: process.env values should be defined from config.env and .env

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: thehabes

.github/workflows/cd_dev.yaml

@@ -80,7 +80,7 @@ jobs:
           git checkout development
           git pull
           npm install
-          pm2 -s start -i max bin/tpen3_services.js
+          pm2 start ecosystem.config.js --env development
       - name: Wait for service to be ready
         run: sleep 5
       - name: Run smoke tests

.github/workflows/cd_prod.yaml

@@ -80,7 +80,7 @@ jobs:
           git checkout main
           git pull
           npm install
-          pm2 -s start -i max bin/tpen3_services.js
+          pm2 start ecosystem.config.js --env production
       - name: Wait for service to be ready
         run: sleep 5
       - name: Run smoke tests

ecosystem.config.js

@@ -0,0 +1,43 @@
+/**
+ * PM2 Ecosystem Configuration for TPEN Services
+ *
+ * This configuration ensures that Node.js 22's --env-file flag is properly
+ * passed when running in PM2 cluster mode, allowing config.env and .env
+ * to be loaded correctly.
+ *
+ * Usage:
+ *   pm2 start ecosystem.config.js --env development
+ *   pm2 start ecosystem.config.js --env production
+ */
+
+module.exports = {
+  apps: [
+    {
+      name: 'tpen3-services',
+      script: './bin/tpen3_services.js',
+      instances: 'max',
+      exec_mode: 'cluster',
+      node_args: '--env-file=config.env --env-file=.env',
+      env_development: {
+        NODE_ENV: 'development'
+      },
+      env_production: {
+        NODE_ENV: 'production'
+      },
+      // PM2 cluster mode settings
+      listen_timeout: 10000,
+      kill_timeout: 5000,
+      wait_ready: false,
+      max_memory_restart: '500M',
+      // Logging
+      error_file: './logs/pm2-error.log',
+      out_file: './logs/pm2-out.log',
+      log_date_format: 'YYYY-MM-DD HH:mm:ss Z',
+      merge_logs: true,
+      // Auto-restart settings
+      autorestart: true,
+      max_restarts: 10,
+      min_uptime: '10s'
+    }
+  ]
+};