Implement DALI Bridge Engine and Model Management

- Added `bridge.cpp` to handle DALI bridge operations including model management, command execution, and response formatting.
- Introduced `bridge_model.cpp` for defining bridge models, value transformations, and JSON serialization/deserialization.
- Created `bridge_provisioning.cpp` for managing bridge configuration storage and retrieval using NVS on ESP platform.
- Enhanced `gateway_cloud.cpp` to integrate DALI bridge requests and responses with cloud communication.
- Introduced `modbus_bridge.cpp` to handle Modbus-specific operations and register management.
- Implemented utility functions for converting between DaliValue and cJSON formats.
- Added error handling and metadata management in bridge responses.

include/modbus_bridge.hpp

@@ -0,0 +1,36 @@
+#pragma once
+
+#include "bridge.hpp"
+
+#include <cstdint>
+#include <optional>
+#include <string>
+#include <vector>
+
+struct ModbusBridgeConfig {
+  std::string transport = "tcp";
+  std::string host;
+  uint16_t port = 502;
+  uint8_t unitID = 1;
+};
+
+struct ModbusRegisterBinding {
+  std::string modelID;
+  int registerAddress = -1;
+};
+
+class DaliModbusBridge {
+ public:
+  explicit DaliModbusBridge(DaliBridgeEngine& engine);
+
+  void setConfig(const ModbusBridgeConfig& config);
+  const ModbusBridgeConfig& config() const;
+
+  DaliBridgeResult handleHoldingRegisterWrite(int registerAddress, int value) const;
+  std::optional<ModbusRegisterBinding> findHoldingRegister(int registerAddress) const;
+  std::vector<ModbusRegisterBinding> describeHoldingRegisters() const;
+
+ private:
+  DaliBridgeEngine& engine_;
+  ModbusBridgeConfig config_;
+};