feat(ui): filter for station arrivals after start

lib/api_handler.dart

@@ -202,6 +202,7 @@ class ApiHandler {
     int? fromIdx,
     String? toId,
     int? toIdx,
+    String? startStationId,
   }) async {
     String urlPath = '/api/fahrinfo/latest/journeyDetail';
     Uri url = Uri.https(baseUrl, urlPath, {
@@ -216,7 +217,7 @@ class ApiHandler {
     );
     final httpPackageJson =
         json.decode(jsonResponse.body) as Map<String, dynamic>;
-    final DepartureList = httpPackageJson["Stops"]["Stop"]
+    Iterable<Departure> DepartureList = httpPackageJson["Stops"]["Stop"]
         .map(
           (x) => Departure.fromJson(
             // needed because I'm too lazy to write a second mostly identical
@@ -224,9 +225,17 @@ class ApiHandler {
             _expandDeparturesJson(httpPackageJson, x, ["ref", "Product"]),
           ),
         )
-        .toList()
         .cast<Departure>();
-    return DepartureList;
+
+    // preferably this happens always?
+    if (startStationId != null) {
+      // show Stations after the one we are at
+      return DepartureList.skipWhile(
+        (x) => x.stationId != startStationId,
+      ).skip(1).toList();
+    }
+
+    return DepartureList.toList().cast<Departure>();
   }
 
   // workaround for the fact that json from tripDetail and DepartureBoard are