Add companion radio stats, adaptive backoff, path hash width, and UI improvements

- Companion radio stats: poll and display noise floor, RSSI, SNR, airtime
  with dedicated ValueNotifier and ref-counted polling
- Adaptive RF-aware TX backoff based on radio conditions instead of fixed 5s
- Variable-width path hash support (1-3 bytes per hop)
- Air activity dot indicator in app bar with tap to open stats screen
- Jump to oldest unread setting for chat screens
- 1s send cooldown on DM and channel messages
- Link style: theme-aware orange, added EmailLinkifier
- New languages: Hungarian, Japanese, Korean
- Remove dead DeviceScreen and BatteryIndicatorChip
- Remove wakelock_plus dependency
- TX power fields now read as signed int8

lib/screens/channels_screen.dart

@@ -127,10 +127,7 @@ class _ChannelsScreenState extends State<ChannelsScreen>
       canPop: allowBack,
       child: Scaffold(
         appBar: AppBar(
-          title: AppBarTitle(
-            context.l10n.channels_title,
-            indicators: false,
-          ),
+          title: AppBarTitle(context.l10n.channels_title, indicators: false),
           centerTitle: true,
           automaticallyImplyLeading: false,
           actions: [