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/settings_screen.dart

@@ -275,8 +275,8 @@ class _SettingsScreenState extends State<SettingsScreen> {
             title: Text(l10n.radioStats_settingsTile),
             subtitle: Text(l10n.radioStats_settingsSubtitle),
             trailing: const Icon(Icons.chevron_right),
-            enabled: connector.isConnected &&
-                connector.supportsCompanionRadioStats,
+            enabled:
+                connector.isConnected && connector.supportsCompanionRadioStats,
             onTap: () => pushCompanionRadioStatsScreen(context),
           ),
           const Divider(height: 1),