Notification rate limiting (#110)

* Add notification rate limiting with privacy-safe debug logging

- Add batching system to prevent notification storms (3s rate limit, 5s batch window)
- Queue rapid notifications and show batch summaries
- Debug logs show device names for adverts, sender/channel for messages (no content leaks)
- Remove unused _maxBatchSize constant

Context: Added after getting notification-flooded while evaluating RF flood management. The irony.

* Update notification_service.dart

I made a mistake and removed this

* Add l10n support for notification strings

Addresses PR #110 review feedback to use the translations system:
- Add notification strings to app_en.arb (plurals for batch summary)
- Update NotificationService to use lookupAppLocalizations()
- Wire locale from MaterialApp to NotificationService
- Regenerate localization files

New strings added (English only, translations needed):
- notification_activityTitle: "MeshCore Activity"
- notification_messagesCount: "{count} message(s)"
- notification_channelMessagesCount: "{count} channel message(s)"
- notification_newNodesCount: "{count} new node(s)"
- notification_newTypeDiscovered: "New {type} discovered"
- notification_receivedNewMessage: "Received new message"

* Add notification string translations for all supported languages

Translated notification_activityTitle, notification_messagesCount,
notification_channelMessagesCount, notification_newNodesCount,
notification_newTypeDiscovered, and notification_receivedNewMessage
to: bg, de, es, fr, it, nl, pl, pt, ru, sk, sl, sv, uk, zh

Includes proper ICU plural forms for Slavic languages (few/many/other)
and Slovenian dual form.

* Apply dart format to notification_service.dart

---------

Co-authored-by: Winston Lowe <wel97459@gmail.com>

lib/l10n/app_pt.arb

@@ -1569,6 +1569,13 @@
   "contacts_contactAdvertCopyFailed": "Cópia do anúncio para a Área de Transferência falhou.",
   "contacts_ShareContactZeroHop": "Compartilhar contato por anúncio",
   "contacts_zeroHopContactAdvertFailed": "Falha ao enviar contato.",
+  "notification_activityTitle": "Atividade MeshCore",
+  "notification_messagesCount": "{count} {count, plural, =1{mensagem} other{mensagens}}",
+  "notification_channelMessagesCount": "{count} {count, plural, =1{mensagem de canal} other{mensagens de canal}}",
+  "notification_newNodesCount": "{count} {count, plural, =1{novo nó} other{novos nós}}",
+  "notification_newTypeDiscovered": "Novo {contactType} descoberto",
+  "notification_receivedNewMessage": "Nova mensagem recebida",
+  "contacts_zeroHopContactAdvertFailed": "Falha ao enviar contato.",
   "settings_gpxExportRepeaters": "Exportar repetidores / servidor de sala para GPX",
   "settings_gpxExportRepeatersSubtitle": "Exporta repetidores / roomserver com localização para arquivo GPX.",
   "settings_gpxExportSuccess": "Arquivo GPX exportado com sucesso.",
@@ -1585,4 +1592,5 @@
   "settings_gpxExportShareText": "Dados do mapa exportados do meshcore-open",
   "settings_gpxExportShareSubject": "meshcore-open exportação de dados de mapa GPX",
   "pathTrace_someHopsNoLocation": "Um ou mais dos lúpulos estão sem localização!"
+
 }