Add localization support for German, Spanish, French, and Italian

- Updated localization files for French, Croatian, Italian, Slovenian to include translations for German, Spanish, French, and Italian.
- Added new methods for handling drawing messages sent to the public channel in multiple languages.
- Enhanced the Contact model to identify public channels using a dedicated method.
- Implemented echo detection for public channel messages, including tracking and reporting of echoes.
- Updated BLE response handling to support echo detection and tracking of sent messages.
- Modified UI components to reflect new localization strings and echo statuses.

lib/l10n/app_en.arb

@@ -232,6 +232,26 @@
     "description": "Croatian language option"
   },
 
+  "german": "German",
+  "@german": {
+    "description": "German language option"
+  },
+
+  "spanish": "Spanish",
+  "@spanish": {
+    "description": "Spanish language option"
+  },
+
+  "french": "French",
+  "@french": {
+    "description": "French language option"
+  },
+
+  "italian": "Italian",
+  "@italian": {
+    "description": "Italian language option"
+  },
+
   "locationBroadcasting": "Location Broadcasting",
   "@locationBroadcasting": {
     "description": "Location settings section header"
@@ -639,6 +659,24 @@
     "description": "Description for room storage permanence"
   },
 
+  "drawingsSentToPublicChannel": "Sent {count} map drawing{plural} to Public Channel",
+  "@drawingsSentToPublicChannel": {
+    "description": "System message when drawings are sent to public channel",
+    "placeholders": {
+      "count": {"type": "int"},
+      "plural": {"type": "String"}
+    }
+  },
+
+  "drawingsSharedToPublicChannel": "Shared {success}/{total} drawings to Public Channel",
+  "@drawingsSharedToPublicChannel": {
+    "description": "Snackbar message showing success count for drawings shared to public channel",
+    "placeholders": {
+      "success": {"type": "int"},
+      "total": {"type": "int"}
+    }
+  },
+
   "notConnectedToDevice": "Not connected to device",
   "@notConnectedToDevice": {
     "description": "Error message when device is not connected for direct messaging"
@@ -1715,6 +1753,11 @@
     "description": "Delivery status: failed"
   },
 
+  "broadcast": "Broadcast",
+  "@broadcast": {
+    "description": "Delivery status for channel messages (no echoes yet)"
+  },
+
   "sarMarkerFoundPerson": "Found Person",
   "@sarMarkerFoundPerson": {
     "description": "SAR marker type: found person"