feat: initial myprimal MQTT bridge service

Dynamic MySolem/MyIndygo IoT bridge with MQTT, Home Assistant
autodiscovery, and Homebridge EasyMQTT compatibility.

- Device discovery via MySolem API on startup (all modules/inputs/outputs)
- Configurable poll engine (fast/normal/slow buckets, per-input overrides)
- MQTT retained state publishing + HA autodiscovery payloads
- Unified manual command routing (linesControl vs sendManualModuleCommand)
- Runtime config via MQTT $config/set, persisted to config.json
- Expression override system (API-provided > hardcoded > passthrough)
- Minimal REST API: /health, /state, /control, /rediscover
- Docker deployment (Dockerfile + docker-compose.yml)
- 38 unit tests

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/mqtt/config-bridge.js

@@ -0,0 +1,41 @@
+'use strict';
+const { getClient, getPrefix, publish } = require('./client');
+const { getConfig, patchConfig, on: onConfigChange } = require('../config');
+const poller = require('../poller');
+
+function subscribe() {
+  const client = getClient();
+  if (!client) return;
+  const prefix = getPrefix();
+
+  const setTopic = `${prefix}/$config/set`;
+  client.subscribe(setTopic);
+
+  client.on('message', (topic, buf) => {
+    if (topic !== setTopic) return;
+    let patch;
+    try {
+      patch = JSON.parse(buf.toString());
+    } catch {
+      console.warn('[config-bridge] Invalid JSON on $config/set');
+      return;
+    }
+    patchConfig(patch);
+    console.log('[config-bridge] Config updated:', JSON.stringify(patch));
+  });
+
+  // Republish current config on connect
+  publishConfig();
+
+  // Republish + reload poller when config changes
+  onConfigChange('change', () => {
+    publishConfig();
+    poller.reload();
+  });
+}
+
+function publishConfig() {
+  publish('$config', getConfig());
+}
+
+module.exports = { subscribe, publishConfig };