feat(e2e): 端对端加密完全对齐老项目 — cipher_guard_sdk 修正 + EncryptionManager 集成

修正 cipher_guard_sdk 4 个关键密码学差异使其与老 Flutter 项目 (im-client-im-dev) 和 iOS
EncryptionManager 完全互操作：

1. AES: 显式 SIC/CTR 模式 + 16 zero-byte IV（原 SDK 用随机 IV + KDF 派生密钥）
2. RSA: bare RSAEngine 无 PKCS1 padding（原 SDK 用 PKCS1Encoding）
3. Session key: 32-char alphanumeric ASCII（原 SDK 用 base64 random bytes）
4. Wire format: base64(ciphertext) 无 IV 前缀

新增 EncryptionManager：
- Per-chat round-based key chain（最多 10 rounds/chat，FIFO 淘汰）
- 登录后自动 setup：RSA 密钥对生成/存储 + 公钥上传 + chat 密钥拉取解密
- API 集成：cipher/v2/key/my, key/set, chat/my
- 消息加密返回 JSON envelope {"round":N,"data":"<base64>"}
- 消息解密兼容 JSON envelope + legacy raw base64

集成到消息流：
- SendMessageUseCase: 发送前加密 content → wireContent
- WsMessageService: 收到消息后解密 content + lastMsg
- 无密钥时 fallback 到明文（对齐 iOS 行为）

注意：/app/api/cipher/v2/key/set 仍为预发布接口，仅测试阶段使用

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/im_app/lib/data/remote/cipher_api_requests.dart

@@ -0,0 +1,170 @@
+import 'package:networks_sdk/networks_sdk.dart';
+
+/// 对齐老项目 /app/api/cipher/v2/* API 端点
+///
+/// /app/api/cipher/v2/key/set 是预发布接口，仅测试阶段使用。
+
+// ── GET /app/api/cipher/v2/key/my — 获取自己的公钥 ────────────────────────
+
+class CipherMyKeyResponse {
+  final String publicKey;
+  final String? encPrivate;
+  final int? uid;
+
+  const CipherMyKeyResponse({
+    required this.publicKey,
+    this.encPrivate,
+    this.uid,
+  });
+
+  factory CipherMyKeyResponse.fromJson(Map<String, dynamic> json) =>
+      CipherMyKeyResponse(
+        publicKey: (json['public_key'] ?? '') as String,
+        encPrivate: json['enc_pk'] as String?,
+        uid: json['uid'] as int?,
+      );
+}
+
+class CipherGetMyKeyRequest extends ApiRequestable<CipherMyKeyResponse?> {
+  @override
+  String get path => '/app/api/cipher/v2/key/my';
+
+  @override
+  HttpMethod get method => HttpMethod.get;
+
+  @override
+  Map<String, dynamic> get parameters => {};
+
+  @override
+  CipherMyKeyResponse? decodeResponse(dynamic response) {
+    final data = (response as dynamic).data;
+    if (data is! Map<String, dynamic>) return null;
+    return CipherMyKeyResponse.fromJson(data);
+  }
+}
+
+// ── POST /app/api/cipher/v2/key/set — 上传公钥 ─────────────────────────────
+
+class CipherSetKeyRequest extends ApiRequestable<void> {
+  final String publicKey;
+  final String encPk;
+
+  CipherSetKeyRequest({required this.publicKey, required this.encPk});
+
+  @override
+  String get path => '/app/api/cipher/v2/key/set';
+
+  @override
+  HttpMethod get method => HttpMethod.post;
+
+  @override
+  Map<String, dynamic> get parameters => {
+        'public_key': publicKey,
+        'enc_pk': encPk,
+      };
+
+  @override
+  void decodeResponse(dynamic response) {}
+}
+
+// ── GET /app/api/cipher/v2/chat/my — 获取所有聊天的加密密钥 ─────────────────
+
+class CipherChatKeyItem {
+  final int? chatId;
+  final String? session;
+  final int? round;
+
+  const CipherChatKeyItem({this.chatId, this.session, this.round});
+
+  factory CipherChatKeyItem.fromJson(Map<String, dynamic> json) =>
+      CipherChatKeyItem(
+        chatId: json['chat_id'] as int?,
+        session: json['session'] as String?,
+        round: json['round'] as int?,
+      );
+}
+
+class CipherGetMyChatKeysRequest
+    extends ApiRequestable<List<CipherChatKeyItem>?> {
+  @override
+  String get path => '/app/api/cipher/v2/chat/my';
+
+  @override
+  HttpMethod get method => HttpMethod.get;
+
+  @override
+  Map<String, dynamic> get parameters => {};
+
+  @override
+  List<CipherChatKeyItem>? decodeResponse(dynamic response) {
+    final data = (response as dynamic).data;
+    if (data is! List) return null;
+    return data
+        .cast<Map<String, dynamic>>()
+        .map(CipherChatKeyItem.fromJson)
+        .toList();
+  }
+}
+
+// ── GET /app/api/cipher/v2/key/gets — 获取其他用户的公钥 ─────────────────────
+
+class CipherUserKeyResponse {
+  final int? uid;
+  final String? publicKey;
+
+  const CipherUserKeyResponse({this.uid, this.publicKey});
+
+  factory CipherUserKeyResponse.fromJson(Map<String, dynamic> json) =>
+      CipherUserKeyResponse(
+        uid: json['uid'] as int?,
+        publicKey: json['public_key'] as String?,
+      );
+}
+
+class CipherGetUsersKeysRequest
+    extends ApiRequestable<List<CipherUserKeyResponse>?> {
+  final List<int> userIds;
+
+  CipherGetUsersKeysRequest({required this.userIds});
+
+  @override
+  String get path => '/app/api/cipher/v2/key/gets';
+
+  @override
+  HttpMethod get method => HttpMethod.get;
+
+  @override
+  Map<String, dynamic> get parameters => {
+        'uids': userIds.join(','),
+      };
+
+  @override
+  List<CipherUserKeyResponse>? decodeResponse(dynamic response) {
+    final data = (response as dynamic).data;
+    if (data is! List) return null;
+    return data
+        .cast<Map<String, dynamic>>()
+        .map(CipherUserKeyResponse.fromJson)
+        .toList();
+  }
+}
+
+// ── POST /app/api/cipher/v2/chat/update — 更新聊天加密密钥 ──────────────────
+
+class CipherUpdateChatKeysRequest extends ApiRequestable<void> {
+  final List<Map<String, dynamic>> sessions;
+
+  CipherUpdateChatKeysRequest({required this.sessions});
+
+  @override
+  String get path => '/app/api/cipher/v2/chat/update';
+
+  @override
+  HttpMethod get method => HttpMethod.post;
+
+  @override
+  Map<String, dynamic> get parameters => {'sessions': sessions};
+
+  @override
+  void decodeResponse(dynamic response) {}
+}