Initial commit: LAN Checker

Network health monitoring script with MQTT reporting for Home Assistant.
- Ping, HTTP, and SNMP checkers
- MQTT Discovery for automatic entity creation
- Configurable check intervals

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

CLAUDE.md

@@ -0,0 +1,39 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+LAN Checker is a Python script that monitors network services and devices, publishing status via MQTT to Home Assistant using MQTT Discovery.
+
+## Commands
+
+```bash
+# Install dependencies
+pip install -r requirements.txt
+
+# Setup config
+cp config.yaml.example config.yaml
+
+# Run
+python lan_checker.py
+```
+
+## Architecture
+
+- `lan_checker.py` - Main script: config loading, MQTT client, check scheduler
+- `checkers/` - Modular check implementations
+  - `base.py` - `BaseChecker` abstract class and `CheckResult` dataclass
+  - `ping.py`, `http.py`, `snmp.py` - Concrete checker implementations
+- `config.yaml.example` - Configuration template (copy to `config.yaml`)
+
+## Adding a New Checker
+
+1. Create `checkers/newtype.py` inheriting from `BaseChecker`
+2. Implement `check()` method returning `CheckResult`
+3. Register in `checkers/__init__.py` CHECKERS dict
+
+## MQTT Topics
+
+- Discovery: `homeassistant/binary_sensor/lan_checker_{id}/config`
+- State: `lan_checker/{id}/state` (JSON with state, message, response_time, last_check)