feat: implement MailGun webhook service for logging email events

Implemented a production-ready TypeScript/Express.js service to receive
and log MailGun webhook events (delivered, failed, opened, clicked, etc.).

Key features:
- Webhook endpoint (POST /webhook) with comprehensive event logging
- Full TypeScript type definitions for all MailGun event types
- Prometheus metrics integration for monitoring
- Health check endpoint (GET /ping)
- Comprehensive Jest test suite with 87.76% coverage
- Docker containerization with build scripts

Removed template/example code:
- All SQL/MSSQL dependencies and related code
- Example auth router and middleware
- PRTG metrics support (simplified to Prometheus only)
- Unused middleware (CORS, IP whitelist, request parsing/validation)
- Template documentation (kept only MailGun webhook API spec)

The service is clean, minimal, and focused solely on receiving and
logging MailGun webhook events to the console.

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

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

mailgun-webhook/.vscode/launch.json

@@ -0,0 +1,61 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Debug Server",
+            "type": "node",
+            "request": "launch",
+            "envFile": "${workspaceFolder}/.env",
+            "skipFiles": [
+                "<node_internals>/**"
+            ],
+            "runtimeExecutable": "npm",
+            "runtimeArgs": [
+                "run-script",
+                "start"
+            ],
+            "sourceMaps": true,
+            "env": {
+                "DEBUG": "*"
+            }
+        },
+        {
+            "type": "node",
+            "name": "vscode-jest-tests",
+            "request": "launch",
+            "envFile": "${workspaceFolder}/.env",
+            "console": "integratedTerminal",
+            "internalConsoleOptions": "neverOpen",
+            "cwd": "${workspaceFolder}",
+            "runtimeExecutable": "npm",
+            "args": [
+                "run",
+                "test",
+                "--",
+                "--runInBand",
+                "--watchAll=false"
+            ]
+        },
+        {
+            "type": "node",
+            "name": "vscode-jest-tests-1634200842588",
+            "request": "launch",
+            "envFile": "${workspaceFolder}/.env",
+            "console": "integratedTerminal",
+            "internalConsoleOptions": "neverOpen",
+            "cwd": "${workspaceFolder}",
+            "runtimeExecutable": "npm",
+            "args": [
+                "run",
+                "test",
+                "--",
+                "--runInBand",
+                "--watchAll=false"
+            ]
+        },
+
+    ]
+}