feat: add Codec2 voice messages over LoRa mesh (iOS/macOS only)

Push-to-talk voice messaging using the Codec2 ultra-low-bitrate speech
codec, transmitted as V: prefixed packets over the existing MeshCore
LoRa mesh pipeline.

Voice recording UI (long-press send button or + menu) is gated behind
Platform.isIOS || Platform.isMacOS since the `record` package only
supports microphone capture on those platforms in this build.

Key changes:
- VoiceRecorderService: streams 8kHz mono PCM chunks via `record` package
- VoicePlayerService: decodes Codec2 bytes to WAV and plays via audioplayers
- VoiceCodecService: async Codec2 encode/decode in background isolates
- VoiceProvider: reassembles multi-packet sessions, drives playback
- VoiceMessageBubble: shows packet progress, play/stop controls
- MessagesProvider: detects V: prefix, routes to VoiceProvider
- MessagesTab: PTT long-press gesture + recording indicator (iOS/macOS)
- Message model: isVoice + voiceId fields for session tracking
- Auto-selects codec mode from radio bandwidth (700C/1200/1300 bps)
- codec2_flutter + meshcore_client switched from path to git deps

linux/flutter/generated_plugin_registrant.cc

@@ -6,13 +6,21 @@
 
 #include "generated_plugin_registrant.h"
 
+#include <audioplayers_linux/audioplayers_linux_plugin.h>
 #include <objectbox_flutter_libs/objectbox_flutter_libs_plugin.h>
+#include <record_linux/record_linux_plugin.h>
 #include <url_launcher_linux/url_launcher_plugin.h>
 
 void fl_register_plugins(FlPluginRegistry* registry) {
+  g_autoptr(FlPluginRegistrar) audioplayers_linux_registrar =
+      fl_plugin_registry_get_registrar_for_plugin(registry, "AudioplayersLinuxPlugin");
+  audioplayers_linux_plugin_register_with_registrar(audioplayers_linux_registrar);
   g_autoptr(FlPluginRegistrar) objectbox_flutter_libs_registrar =
       fl_plugin_registry_get_registrar_for_plugin(registry, "ObjectboxFlutterLibsPlugin");
   objectbox_flutter_libs_plugin_register_with_registrar(objectbox_flutter_libs_registrar);
+  g_autoptr(FlPluginRegistrar) record_linux_registrar =
+      fl_plugin_registry_get_registrar_for_plugin(registry, "RecordLinuxPlugin");
+  record_linux_plugin_register_with_registrar(record_linux_registrar);
   g_autoptr(FlPluginRegistrar) url_launcher_linux_registrar =
       fl_plugin_registry_get_registrar_for_plugin(registry, "UrlLauncherPlugin");
   url_launcher_plugin_register_with_registrar(url_launcher_linux_registrar);

linux/flutter/generated_plugins.cmake

@@ -3,7 +3,9 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  audioplayers_linux
   objectbox_flutter_libs
+  record_linux
   url_launcher_linux
 )