feat: add email-server-worker with clean template architecture

Add new email-server-worker project implementing a self-scheduling background worker pattern with HTTP monitoring. Removed all business-specific code from copied source, creating a clean, reusable template.

Key features:
- Self-scheduling worker loop with configurable interval
- Graceful shutdown support (Docker-compatible)
- Prometheus metrics collection
- Health check endpoints (/healthcheck, /metrics, /ping)
- Example worker template for easy customization
- Comprehensive architecture documentation in CLAUDE.md

The worker is now ready for email server implementation with no external dependencies on Evolution/MSSQL/ElasticSearch.

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

email-server-worker/README.md

@@ -1,27 +1,115 @@
 # Email Server Worker
 
-This workspace contains the email server worker service for the Evidencija Režija tenant notification system.
+Background worker service with HTTP health monitoring and metrics collection.
 
-## Purpose
+## Overview
 
-This service manages email operations by:
-- Polling MongoDB for email status changes
-- Detecting unverified tenant emails (EmailStatus.Unverified)
-- Sending verification emails to tenants
-- Updating email status to VerificationPending
-- Sending scheduled notifications (rent due, utility bills)
+This is a TypeScript-based background worker service that combines periodic task execution with HTTP health monitoring and metrics collection. It implements a self-scheduling worker pattern with graceful shutdown support.
 
-## Architecture
+## Features
 
-This is a standalone background worker service that:
-- Runs independently from the Next.js web-app
-- Communicates via the shared MongoDB database
-- Integrates with email service provider (e.g., Mailgun, SendGrid)
+- **Periodic Task Execution**: Self-scheduling worker loop with configurable interval
+- **Graceful Shutdown**: Ensures in-flight work completes before shutdown (Docker-compatible)
+- **Health Monitoring**: HTTP health check endpoint to verify worker status
+- **Metrics Collection**: Prometheus metrics with PRTG adapter
+- **Error Isolation**: Worker errors don't crash the process
 
-## Setup
+## Getting Started
 
-TBD
+### Installation
+
+```bash
+npm install
+```
+
+### Development
+
+```bash
+npm run start  # Start with nodemon (auto-reload)
+```
+
+### Build & Run
+
+```bash
+npm run build      # Compile TypeScript
+npm run run-server # Run compiled version
+```
+
+### Testing
+
+```bash
+npm run test  # Run Jest in watch mode
+```
 
 ## Environment Variables
 
-TBD
+### Required
+
+- `PULL_INTERVAL` - Milliseconds between work cycles (default: `"10000"`)
+
+### Optional
+
+- `PORT` - HTTP server port (default: `"3000"`)
+- `PROMETHEUS_APP_LABEL` - App label for Prometheus metrics (default: `"email-server-worker"`)
+- `PROMETHEUS_HISTOGRAM_BUCKETS` - Histogram bucket sizes (default: `"0.1, 0.5, 1, 5, 10"`)
+- `DEBUG` - Debug namespaces for console logging (e.g., `"server:server"`)
+- `ENV` - Environment mode: `"dev"`, `"jest"` (affects logging)
+
+## HTTP Endpoints
+
+- `GET /healthcheck` - Health check endpoint (verifies worker is running)
+- `GET /metrics` - Prometheus metrics
+- `GET /prtg` - PRTG-compatible metrics (XML format)
+- `GET /ping` - Simple ping/pong endpoint
+
+## Creating a Worker
+
+See `src/exampleWorker.ts` for the worker template. The worker must export a `doWork` function:
+
+```typescript
+
+export const doWork = async () => {
+  // Your periodic task logic here
+  logger.info("Task Completed", "Work done successfully");
+
+  // Throw errors to mark as failed:
+  // throw new Error("Something went wrong");
+};
+```
+
+Update `src/workRunner.ts` line 6 to import your worker:
+
+```typescript
+import { doWork } from "./yourWorker";
+```
+
+## Architecture
+
+- **entry.ts** - HTTP server setup, signal handling, worker lifecycle
+- **workRunner.ts** - Self-scheduling loop, metrics, graceful shutdown
+- **app.ts** - Express app configuration, routes
+- **src/lib/** - Shared utilities (logger, metrics, etc.)
+- **src/routes/** - HTTP route handlers
+
+## Deployment
+
+The service uses the `stoppable` library for graceful shutdown with a 10-second timeout before force-closing connections. Docker containers will receive SIGTERM signals and shut down gracefully.
+
+## Logging
+
+The service supports two logging mechanisms:
+
+1. **Console Logging**: Uses the `debug` package, controlled by `DEBUG` env variable
+
+## Metrics
+
+Prometheus metrics are automatically collected:
+
+- `request_operations_total` - Total work cycles executed
+- `request_operations_ok` - Successful work cycles
+- `request_operations_failed` - Failed work cycles
+- `request_duration_seconds` - Duration histogram of work cycles
+
+## Documentation
+
+See `CLAUDE.md` in the repository root for complete architecture documentation and guidance.