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/app_settings_screen.dart

@@ -294,9 +294,7 @@ class AppSettingsScreen extends StatelessWidget {
           SwitchListTile(
             secondary: const Icon(Icons.vertical_align_top),
             title: Text(context.l10n.appSettings_jumpToOldestUnread),
-            subtitle: Text(
-              context.l10n.appSettings_jumpToOldestUnreadSubtitle,
-            ),
+            subtitle: Text(context.l10n.appSettings_jumpToOldestUnreadSubtitle),
             value: settingsService.settings.jumpToOldestUnread,
             onChanged: settingsService.setJumpToOldestUnread,
           ),