image querying from within the frontend

frontend/lib/structs/landmark.dart

@@ -24,8 +24,7 @@ final class Landmark extends LinkedListEntry<Landmark>{
   // description to be shown in the overview
   final String? nameEN;
   final String? websiteURL;
-  final String? wikipediaURL;
-  final String? imageURL;
+  String? imageURL; // not final because it can be patched
   final String? description;
   final Duration? duration;
   final bool? visited;
@@ -44,7 +43,6 @@ final class Landmark extends LinkedListEntry<Landmark>{
 
     this.nameEN,
     this.websiteURL,
-    this.wikipediaURL,
     this.imageURL,
     this.description,
     this.duration,
@@ -70,7 +68,6 @@ final class Landmark extends LinkedListEntry<Landmark>{
       final isSecondary = json['is_secondary'] as bool?;
       final nameEN = json['name_en'] as String?;
       final websiteURL = json['website_url'] as String?;
-      final wikipediaURL = json['wikipedia_url'] as String?;
       final imageURL = json['image_url'] as String?;
       final description = json['description'] as String?;
       var duration = Duration(minutes: json['duration'] ?? 0) as Duration?;
@@ -85,7 +82,6 @@ final class Landmark extends LinkedListEntry<Landmark>{
         isSecondary: isSecondary,
         nameEN: nameEN,
         websiteURL: websiteURL,
-        wikipediaURL: wikipediaURL,
         imageURL: imageURL,
         description: description,
         duration: duration,
@@ -112,7 +108,6 @@ final class Landmark extends LinkedListEntry<Landmark>{
     'is_secondary': isSecondary,
     'name_en': nameEN,
     'website_url': websiteURL,
-    'wikipedia_url': wikipediaURL,
     'image_url': imageURL,
     'description': description,
     'duration': duration?.inMinutes,