refactor(app): remove unsupported server selector state (#6)

Remove UI and provider state that does not control the authoritative tunnel destination while preserving the existing connection-health status behavior.

lib/logic/server_list.dart

@@ -1,69 +0,0 @@
-import 'package:flutter/foundation.dart';
-import 'package:shared_preferences/shared_preferences.dart';
-
-// ── lib/logic/server_list.dart ──────────────────────────────────────────────
-// Server data model and ChangeNotifier — shared by StatusBar (shows current
-// server name/flag) and SelectionScreen (lets user pick a server).
-//
-// Each server is defined by its tunnel IP/port. Reality credentials (public
-// key, shortId) come from /session/status per session; only the transport
-// parameters live in AppConfig.
-//
-// When multi-server ships:
-//   - _all becomes a fetched list (from /api/servers or bundled config)
-//   - SelectionScreen shows multiple rows
-//   - select() triggers a disconnect/reconnect cycle if the tunnel is active
-
-class ServerInfo {
-  final String id;
-  final String name;
-  final String flagAsset;
-  final String ip;
-  final int port;
-
-  const ServerInfo({
-    required this.id,
-    required this.name,
-    required this.flagAsset,
-    required this.ip,
-    required this.port,
-  });
-}
-
-class ServerList extends ChangeNotifier {
-  static const _all = [
-    ServerInfo(
-      id: 'finland',
-      name: 'Helsinki, Finland',
-      flagAsset: 'assets/finland_flag_256.png',
-      ip: '204.168.246.88',
-      port: 443,
-    ),
-  ];
-
-  int _selectedIndex = 0;
-
-  List<ServerInfo> get all => _all;
-  int get selectedIndex => _selectedIndex;
-  ServerInfo get selected => _all[_selectedIndex];
-
-  // Loads persisted selection from SharedPreferences.
-  // Fire-and-forget — UI starts with default, updates when prefs load.
-  Future<void> init() async {
-    final prefs = await SharedPreferences.getInstance();
-    final saved = prefs.getInt('selected_server_index') ?? 0;
-    if (saved >= 0 && saved < _all.length && saved != _selectedIndex) {
-      _selectedIndex = saved;
-      notifyListeners();
-    }
-  }
-
-  // Switches to a different server. Persists the choice.
-  Future<void> select(int index) async {
-    if (index == _selectedIndex || index < 0 || index >= _all.length) return;
-    _selectedIndex = index;
-    notifyListeners();
-    final prefs = await SharedPreferences.getInstance();
-    await prefs.setInt('selected_server_index', index);
-  }
-}