feat: Add setting to disable map tab for battery savings

Add a new "Disable Map" toggle in settings that allows users to hide
the map tab entirely. This is useful for scenarios where the map is
not needed and battery conservation is a priority.

Changes:
- Add disableMap and disableMapDescription localized strings (all languages)
- Add isMapEnabled state to AppProvider with persistence
- Update HomeScreen to dynamically adjust tab count based on setting
- Make onNavigateToMap optional in MessagesTab and ContactsTab
- Add toggle switch in Settings screen under Interface section

lib/l10n/app_de.arb

@@ -217,6 +217,16 @@
     "description": "Beschreibung für die Einstellung des einfachen Modus"
   },
 
+  "disableMap": "Karte deaktivieren",
+  "@disableMap": {
+    "description": "Einstellung zum Deaktivieren des Karten-Tabs"
+  },
+
+  "disableMapDescription": "Karten-Tab ausblenden, um Akku zu sparen",
+  "@disableMapDescription": {
+    "description": "Beschreibung für die Einstellung zum Deaktivieren der Karte"
+  },
+
   "language": "Sprache",
   "@language": {
     "description": "Beschriftung der Spracheinstellung"