Add cloud bridge and provisioning support for ESP32 gateway

- Introduced DaliCloudBridge for MQTT communication with backend.
- Added GatewayProvisioningStore for persisting cloud connection settings using NVS.
- Updated CMakeLists.txt to include new source files.
- Enhanced README.md with usage examples and configuration details.

README.md

@@ -47,3 +47,74 @@ std::vector<int> rgb = dali.dt8.getColourRGB(5);
 - Optional query support: provide a `transact` callback that returns the gateway reply; otherwise, query methods return `std::nullopt`.
 - `Dali` facade in `include/dali.hpp` mirrors `lib/dali/dali.dart` and wires `base`, `decode`, `dt1`, `dt8`, and `addr` together.
 - The `t`, `d`, and `g` parameters in Dart are not required here; timing/gateway selection is driven by your callbacks.
+
+## Cloud Bridge (ESP32 Gateway)
+
+The component now includes `DaliCloudBridge` in `include/gateway_cloud.hpp` to connect ESP32 gateways to the backend MQTT broker.
+
+### Topics
+
+- Downlink: `devices/<deviceID>/down`
+- Uplink: `devices/<deviceID>/up`
+- Status: `devices/<deviceID>/status`
+- Register: `devices/<deviceID>/register`
+
+### Downlink JSON Envelope
+
+```json
+{
+  "type": "dali_cmd",
+  "seq": "123",
+  "op": "send|send_ext|query",
+  "addr": 5,
+  "cmd": 160
+}
+```
+
+### Uplink JSON Envelope
+
+```json
+{
+  "type": "dali_resp",
+  "seq": "123",
+  "op": "query",
+  "ok": true,
+  "data": 255
+}
+```
+
+### Usage
+
+```cpp
+GatewayCloudConfig cfg;
+cfg.brokerURI = "mqtt://192.168.1.100:1883";
+cfg.deviceID = "A1B2C3D4E5F6";
+cfg.username = "device";
+cfg.password = "A1B2C3D4E5F6";
+
+DaliCloudBridge bridge(comm);
+if (bridge.start(cfg)) {
+  bridge.publishStatus("online");
+}
+```
+
+### Provisioning via NVS
+
+Use `GatewayProvisioningStore` to persist cloud connection settings:
+
+```cpp
+GatewayProvisioningStore store;
+GatewayCloudConfig cfg;
+cfg.brokerURI = "mqtt://192.168.1.100:1883";
+cfg.deviceID = "A1B2C3D4E5F6";
+cfg.username = "device";
+cfg.password = "A1B2C3D4E5F6";
+
+store.save(cfg);
+
+GatewayCloudConfig loaded;
+if (store.load(&loaded) == ESP_OK) {
+  DaliCloudBridge bridge(comm);
+  bridge.start(loaded);
+}
+```