Add network monitoring, dashboard, and Home Assistant MQTT publishing

Keep /alive unchanged and serve a dashboard at / with status cards,
latency graphs, an event timeline, and a Wi-Fi section.

Background monitors on configurable intervals: TCP reachability,
DNS resolution, public IP change detection, host reboot detection,
Wi-Fi link quality, and Wi-Fi scan of networks in range via iw.
The Wi-Fi interface is selected with WIFI_INTERFACE; the page lists
visible interfaces and reports when none is available. Scan results
stay in memory, other metrics go to SQLite on a mounted volume.

Optional MQTT publishing with Home Assistant discovery groups all
sensors under one device per host.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TdvJYoY8kc8bmBck89U2i6

hamqtt.py

@@ -0,0 +1,135 @@
+import json
+import logging
+
+import paho.mqtt.client as mqtt
+
+log = logging.getLogger(__name__)
+
+VERSION = "2.0.0"
+
+CONNECTIVITY = {"device_class": "connectivity"}
+
+SENSORS = [
+    ("internet_up", "binary_sensor", "Internet", CONNECTIVITY),
+    ("internet_latency_ms", "sensor", "Internet latency",
+     {"unit_of_measurement": "ms", "state_class": "measurement", "icon": "mdi:timer-outline"}),
+    ("dns_up", "binary_sensor", "DNS", CONNECTIVITY),
+    ("dns_latency_ms", "sensor", "DNS latency",
+     {"unit_of_measurement": "ms", "state_class": "measurement", "icon": "mdi:dns"}),
+    ("public_ip", "sensor", "Public IP", {"icon": "mdi:ip-network-outline"}),
+    ("uptime_s", "sensor", "Host uptime",
+     {"device_class": "duration", "unit_of_measurement": "s", "entity_category": "diagnostic"}),
+]
+
+WIFI_SENSORS = [
+    ("wifi_connected", "binary_sensor", "Wi-Fi", CONNECTIVITY),
+    ("wifi_ssid", "sensor", "Wi-Fi SSID", {"icon": "mdi:wifi"}),
+    ("wifi_signal_dbm", "sensor", "Wi-Fi signal",
+     {"device_class": "signal_strength", "unit_of_measurement": "dBm", "state_class": "measurement"}),
+    ("wifi_tx_bitrate_mbps", "sensor", "Wi-Fi TX bitrate",
+     {"device_class": "data_rate", "unit_of_measurement": "Mbit/s", "state_class": "measurement"}),
+    ("wifi_bssid", "sensor", "Wi-Fi BSSID", {"icon": "mdi:access-point", "entity_category": "diagnostic"}),
+    ("wifi_channel", "sensor", "Wi-Fi channel", {"icon": "mdi:radio-tower", "entity_category": "diagnostic"}),
+    ("wifi_ap_count", "sensor", "Wi-Fi networks in range",
+     {"icon": "mdi:access-point-network", "state_class": "measurement"}),
+]
+
+
+def flatten(snapshot):
+    link = snapshot.get("wifi_link") or {}
+    scan = snapshot.get("wifi_scan") or {}
+    return {
+        "internet_up": snapshot.get("internet_up"),
+        "internet_latency_ms": snapshot.get("internet_latency_ms"),
+        "dns_up": snapshot.get("dns_up"),
+        "dns_latency_ms": snapshot.get("dns_latency_ms"),
+        "public_ip": snapshot.get("public_ip"),
+        "uptime_s": snapshot.get("uptime_s"),
+        "wifi_connected": link.get("connected"),
+        "wifi_ssid": link.get("ssid"),
+        "wifi_bssid": link.get("bssid"),
+        "wifi_signal_dbm": link.get("signal_dbm"),
+        "wifi_tx_bitrate_mbps": link.get("tx_bitrate_mbps"),
+        "wifi_channel": link.get("channel"),
+        "wifi_ap_count": scan.get("count"),
+    }
+
+
+class HomeAssistantPublisher:
+    def __init__(self, cfg):
+        self.cfg = cfg
+        self.node = f"healthcheck_{cfg.device_id}"
+        base = f"healthcheck/{cfg.device_id}"
+        self.state_topic = f"{base}/state"
+        self.availability_topic = f"{base}/availability"
+        self.status_topic = f"{cfg.mqtt_discovery_prefix}/status"
+        self._last_payload = None
+
+        self.client = mqtt.Client(mqtt.CallbackAPIVersion.VERSION2, client_id=self.node)
+        if cfg.mqtt_username:
+            self.client.username_pw_set(cfg.mqtt_username, cfg.mqtt_password)
+        self.client.will_set(self.availability_topic, "offline", retain=True)
+        self.client.on_connect = self._on_connect
+        self.client.on_message = self._on_message
+        self.client.on_disconnect = self._on_disconnect
+
+    def start(self):
+        self.client.reconnect_delay_set(min_delay=2, max_delay=60)
+        self.client.connect_async(self.cfg.mqtt_host, self.cfg.mqtt_port, keepalive=60)
+        self.client.loop_start()
+        log.info("MQTT: connecting to %s:%s as %s", self.cfg.mqtt_host, self.cfg.mqtt_port, self.node)
+
+    def publish_state(self, snapshot):
+        payload = flatten(snapshot)
+        if payload == self._last_payload:
+            return
+        self._last_payload = payload
+        self.client.publish(self.state_topic, json.dumps(payload), retain=True)
+
+    def _on_connect(self, client, userdata, flags, reason_code, properties):
+        if reason_code.is_failure:
+            log.warning("MQTT: connection refused: %s", reason_code)
+            return
+        log.info("MQTT: connected")
+        client.subscribe(self.status_topic)
+        self._announce()
+        if self._last_payload is not None:
+            client.publish(self.state_topic, json.dumps(self._last_payload), retain=True)
+
+    def _on_disconnect(self, client, userdata, flags, reason_code, properties):
+        log.warning("MQTT: disconnected: %s", reason_code)
+
+    def _on_message(self, client, userdata, message):
+        if message.topic == self.status_topic and message.payload.decode(errors="ignore") == "online":
+            log.info("MQTT: Home Assistant came online, re-announcing")
+            self._announce()
+
+    def _announce(self):
+        device = {
+            "identifiers": [self.node],
+            "name": self.cfg.device_name,
+            "model": "healthcheck-container",
+            "manufacturer": "healthcheck",
+            "sw_version": VERSION,
+        }
+        sensors = SENSORS + (WIFI_SENSORS if self.cfg.wifi_interface else [])
+        for key, component, name, extra in sensors:
+            if component == "binary_sensor":
+                template = (
+                    f"{{{{ 'None' if value_json.{key} is none "
+                    f"else ('ON' if value_json.{key} else 'OFF') }}}}"
+                )
+            else:
+                template = f"{{{{ value_json.{key} }}}}"
+            payload = {
+                "name": name,
+                "unique_id": f"{self.node}_{key}",
+                "state_topic": self.state_topic,
+                "value_template": template,
+                "availability_topic": self.availability_topic,
+                "device": device,
+                **extra,
+            }
+            topic = f"{self.cfg.mqtt_discovery_prefix}/{component}/{self.node}/{key}/config"
+            self.client.publish(topic, json.dumps(payload), retain=True)
+        self.client.publish(self.availability_topic, "online", retain=True)