Consolidate BufferReader/Writer, add response validation for repeater settings

- Move BufferReader/BufferWriter into meshcore_protocol.dart
- Refactor build functions to use BufferWriter
- Add content-based validation for CLI responses over LoRa
- Add individual refresh buttons for TX power and feature toggles
- Hide unimplemented features (Privacy Mode, Encrypted Advert Interval)

lib/helpers/buffer_reader.dart

@@ -1,103 +0,0 @@
-import 'dart:convert';
-import 'dart:typed_data';
-
-class BufferReader {
-  int pointer = 0;
-  final Uint8List buffer;
-
-  BufferReader(Uint8List data) : buffer = Uint8List.fromList(data);
-
-  int getRemainingBytesCount() {
-    return buffer.length - pointer;
-  }
-
-  int readByte() {
-    return readBytes(1)[0];
-  }
-
-  Uint8List readBytes(int count) {
-    final data = buffer.sublist(pointer, pointer + count);
-    pointer += count;
-    return data;
-  }
-
-  Uint8List readRemainingBytes() {
-    return readBytes(getRemainingBytesCount());
-  }
-
-  String readString() {
-    return utf8.decode(readRemainingBytes());
-  }
-
-  String readCString(int maxLength) {
-    final value = <int>[];
-    final bytes = readBytes(maxLength);
-    for (final byte in bytes) {
-      // if we find a null terminator character, we have reached the end of the cstring
-      if (byte == 0) {
-        return utf8.decode(Uint8List.fromList(value));
-      }
-      value.add(byte);
-    }
-    return utf8.decode(Uint8List.fromList(value));
-  }
-
-  int readInt8() {
-    final bytes = readBytes(1);
-    return ByteData.view(bytes.buffer).getInt8(0);
-  }
-
-  int readUInt8() {
-    final bytes = readBytes(1);
-    return ByteData.view(bytes.buffer).getUint8(0);
-  }
-
-  int readUInt16LE() {
-    final bytes = readBytes(2);
-    return ByteData.view(bytes.buffer).getUint16(0, Endian.little);
-  }
-
-  int readUInt16BE() {
-    final bytes = readBytes(2);
-    return ByteData.view(bytes.buffer).getUint16(0, Endian.big);
-  }
-
-  int readUInt32LE() {
-    final bytes = readBytes(4);
-    return ByteData.view(bytes.buffer).getUint32(0, Endian.little);
-  }
-
-  int readUInt32BE() {
-    final bytes = readBytes(4);
-    return ByteData.view(bytes.buffer).getUint32(0, Endian.big);
-  }
-
-  int readInt16LE() {
-    final bytes = readBytes(2);
-    return ByteData.view(bytes.buffer).getInt16(0, Endian.little);
-  }
-
-  int readInt16BE() {
-    final bytes = readBytes(2);
-    return ByteData.view(bytes.buffer).getInt16(0, Endian.big);
-  }
-
-  int readInt32LE() {
-    final bytes = readBytes(4);
-    return ByteData.view(bytes.buffer).getInt32(0, Endian.little);
-  }
-
-  int readInt24BE() {
-    // read 24-bit (3 bytes) big endian integer
-    var value = (readByte() << 16) | (readByte() << 8) | readByte();
-
-    // convert 24-bit signed integer to 32-bit signed integer
-    // 0x800000 is the sign bit for a 24-bit value
-    // if it's set, value is negative in 24-bit two's complement
-    if ((value & 0x800000) != 0) {
-      value -= 0x1000000;
-    }
-
-    return value;
-  }
-}

lib/helpers/buffer_writer.dart

@@ -1,57 +0,0 @@
-import 'dart:convert';
-import 'dart:typed_data';
-
-class BufferWriter {
-  final BytesBuilder _builder = BytesBuilder();
-
-  Uint8List toBytes() {
-    return _builder.toBytes();
-  }
-
-  void writeBytes(Uint8List bytes) {
-    _builder.add(bytes);
-  }
-
-  void writeByte(int byte) {
-    _builder.addByte(byte);
-  }
-
-  void writeUInt16LE(int num) {
-    final bytes = Uint8List(2);
-    final data = ByteData.view(bytes.buffer);
-    data.setUint16(0, num, Endian.little);
-    writeBytes(bytes);
-  }
-
-  void writeUInt32LE(int num) {
-    final bytes = Uint8List(4);
-    final data = ByteData.view(bytes.buffer);
-    data.setUint32(0, num, Endian.little);
-    writeBytes(bytes);
-  }
-
-  void writeInt32LE(int num) {
-    final bytes = Uint8List(4);
-    final data = ByteData.view(bytes.buffer);
-    data.setInt32(0, num, Endian.little);
-    writeBytes(bytes);
-  }
-
-  void writeString(String string) {
-    writeBytes(Uint8List.fromList(utf8.encode(string)));
-  }
-
-  void writeCString(String string, int maxLength) {
-    final bytes = Uint8List(maxLength);
-    final encodedString = utf8.encode(string);
-
-    for (var i = 0; i < maxLength && i < encodedString.length; i++) {
-      bytes[i] = encodedString[i];
-    }
-
-    // ensure the last byte is always a null terminator
-    bytes[maxLength - 1] = 0;
-
-    writeBytes(bytes);
-  }
-}

lib/helpers/cayenne_lpp.dart

@@ -1,6 +1,5 @@
 import 'dart:typed_data';
-import 'buffer_reader.dart';
-import 'buffer_writer.dart';
+import '../connector/meshcore_protocol.dart';
 
 class CayenneLpp {
   static const int lppDigitalInput = 0; // 1 byte
@@ -84,7 +83,7 @@ class CayenneLpp {
     final buffer = BufferReader(bytes);
     final telemetry = <Map<String, dynamic>>[];
 
-    while (buffer.getRemainingBytesCount() >= 2) {
+    while (buffer.remaining >= 2) {
       final channel = buffer.readUInt8();
       final type = buffer.readUInt8();
 
@@ -193,7 +192,7 @@ class CayenneLpp {
     final buffer = BufferReader(bytes);
     final Map<int, Map<String, dynamic>> channels = {};
 
-    while (buffer.getRemainingBytesCount() >= 2) {
+    while (buffer.remaining >= 2) {
       final channel = buffer.readUInt8();
       final type = buffer.readUInt8();