Fix lint warnings and cleanup unused code after RadioGroup migration

Remove unused imports, fields, variables, and dead code introduced
during the RadioGroup widget migration and prior changes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/services/deflock_tile_provider.dart

@@ -1,5 +1,4 @@
 import 'dart:async';
-import 'dart:typed_data';
 import 'dart:ui';
 
 import 'package:flutter_map/flutter_map.dart';

lib/services/distance_service.dart

@@ -8,7 +8,6 @@ class DistanceService {
   // Conversion constants
   static const double _metersToFeet = 3.28084;
   static const double _metersToMiles = 0.000621371;
-  static const double _kmToMiles = 0.621371;
 
   /// Format distance for display based on unit preference
   /// 

lib/services/map_data_submodules/nodes_from_osm_api.dart

@@ -7,7 +7,6 @@ import 'package:xml/xml.dart';
 import '../../models/node_profile.dart';
 import '../../models/osm_node.dart';
 import '../../app_state.dart';
-import '../network_status.dart';
 
 /// Fetches surveillance nodes from the direct OSM API using bbox query.
 /// This is a fallback for when Overpass is not available (e.g., sandbox mode).

lib/services/tile_preview_service.dart

@@ -1,5 +1,3 @@
-import 'dart:typed_data';
-
 import 'package:flutter/foundation.dart';
 import 'package:http/http.dart' as http;
 

lib/services/uploader.dart

@@ -54,23 +54,6 @@ class Uploader {
         return UploadResult.failure(errorMessage: errorMsg);
       }
       
-      // Generate changeset XML
-      String action;
-      switch (p.operation) {
-        case UploadOperation.create:
-          action = 'Add';
-          break;
-        case UploadOperation.modify:
-          action = 'Update';
-          break;
-        case UploadOperation.delete:
-          action = 'Delete';
-          break;
-        case UploadOperation.extract:
-          action = 'Extract';
-          break;
-      }
-      
       // Use the user's changeset comment, with XML sanitization
       final sanitizedComment = _sanitizeXmlText(p.changesetComment);
       final csXml = '''