feat: 对齐常驻商城与七鱼客服交互

- 同步商城 H5 登录态与原生 token
- 完善商城/原生 tab 切换、动画及返回交互
- 修复七鱼客服键盘避让和状态栏恢复
- 调整开屏跳过按钮与登录入口交互

lib/features/auth/data/auth_api.dart

@@ -0,0 +1,137 @@
+import 'dart:convert';
+
+import 'package:dio/dio.dart';
+
+import '../../../common/network/dio_provider.dart';
+
+/// 金值账号服务的 protobuf HTTP 契约。
+///
+/// 这个轻量编解码只覆盖短信登录需要的字段，避免把整套历史生成模型带入
+/// 当前重建中的应用；字段号与金值 `account.proto` 保持一致。
+class AuthApi {
+  const AuthApi(this._dio);
+
+  final Dio _dio;
+
+  Future<int> sendSmsCode(String phone) async {
+    final response = await _dio.post<List<int>>(
+      '/api/v1/auth/sms/send',
+      data: _ProtoWriter.stringField(1, phone),
+      options: protobufOptions(),
+    );
+    return _ProtoMessage(response.data ?? const <int>[]).integer(1);
+  }
+
+  Future<AuthLoginResult> verifySmsCode(String phone, String code) async {
+    final response = await _dio.post<List<int>>(
+      '/api/v1/auth/sms/verify',
+      data: [
+        ..._ProtoWriter.stringField(1, phone),
+        ..._ProtoWriter.stringField(2, code),
+      ],
+      options: protobufOptions(),
+    );
+    final reply = _ProtoMessage(response.data ?? const <int>[]);
+    final accessToken = reply.string(1).trim();
+    if (accessToken.isEmpty) {
+      throw const FormatException('登录响应缺少 access_token');
+    }
+    final user = _ProtoMessage(reply.bytes(3));
+    return AuthLoginResult(
+      accessToken: accessToken,
+      phone: user.string(2).trim().isEmpty ? phone : user.string(2).trim(),
+    );
+  }
+}
+
+class AuthLoginResult {
+  const AuthLoginResult({required this.accessToken, required this.phone});
+
+  final String accessToken;
+  final String phone;
+}
+
+class _ProtoWriter {
+  static List<int> stringField(int field, String value) => [
+    ..._varint(field << 3 | 2),
+    ..._varint(utf8.encode(value).length),
+    ...utf8.encode(value),
+  ];
+
+  static List<int> _varint(int value) {
+    final bytes = <int>[];
+    var remaining = value;
+    while (remaining > 0x7f) {
+      bytes.add(remaining & 0x7f | 0x80);
+      remaining >>= 7;
+    }
+    bytes.add(remaining);
+    return bytes;
+  }
+}
+
+class _ProtoMessage {
+  _ProtoMessage(List<int> bytes) : _fields = _parse(bytes);
+
+  final Map<int, Object> _fields;
+
+  int integer(int field) => _fields[field] is int ? _fields[field]! as int : 0;
+
+  String string(int field) => _fields[field] is List<int>
+      ? utf8.decode(_fields[field]! as List<int>, allowMalformed: true)
+      : '';
+
+  List<int> bytes(int field) => _fields[field] is List<int>
+      ? _fields[field]! as List<int>
+      : const <int>[];
+
+  static Map<int, Object> _parse(List<int> bytes) {
+    final fields = <int, Object>{};
+    var cursor = 0;
+    while (cursor < bytes.length) {
+      final tag = _readVarint(bytes, cursor);
+      if (tag == null) break;
+      cursor = tag.next;
+      final field = tag.value >> 3;
+      switch (tag.value & 7) {
+        case 0:
+          final value = _readVarint(bytes, cursor);
+          if (value == null) return fields;
+          fields[field] = value.value;
+          cursor = value.next;
+        case 2:
+          final length = _readVarint(bytes, cursor);
+          if (length == null || length.next + length.value > bytes.length) {
+            return fields;
+          }
+          fields[field] = bytes.sublist(
+            length.next,
+            length.next + length.value,
+          );
+          cursor = length.next + length.value;
+        default:
+          return fields;
+      }
+    }
+    return fields;
+  }
+
+  static _ProtoValue? _readVarint(List<int> bytes, int cursor) {
+    var value = 0;
+    var shift = 0;
+    while (cursor < bytes.length && shift <= 63) {
+      final byte = bytes[cursor++];
+      value |= (byte & 0x7f) << shift;
+      if (byte & 0x80 == 0) return _ProtoValue(value, cursor);
+      shift += 7;
+    }
+    return null;
+  }
+}
+
+class _ProtoValue {
+  const _ProtoValue(this.value, this.next);
+
+  final int value;
+  final int next;
+}