feat(ssh): integrate EncryptionContext into server.rs

SSH加密packet架构集成：

实现内容：
1. server.rs导入EncryptionContext和EncryptedPacket
2. perform_complete_kex_exchange返回EncryptionContext
3. 添加EncryptionContext::default()临时实现

架构集成：
- ✅ EncryptionContext导入完成
- ✅ 密钥交换函数返回加密上下文
- ✅ Default trait实现（临时方案）

编译结果：
- ✅ 编译成功（149 warnings, 0 errors）
- ✅ 架构集成完成

待完善：
- 会话密钥实现（从KexState提取shared_secret）
- IV初始化（从会话密钥派生）
- NEWKEYS后packet切换（使用EncryptedPacket）

技术说明：
- 当前使用临时默认密钥（vec![0u8; 32]）
- 仅用于架构集成和编译验证
- 功能实现待后续完善

markbase-core/src/ssh_server/cipher.rs

@@ -25,6 +25,19 @@ pub struct EncryptionContext {
     pub sequence_number_stoc: u32,     // 服务器→客户端序列号
 }
 
+impl Default for EncryptionContext {
+    fn default() -> Self {
+        Self {
+            encryption_key_ctos: vec![0u8; 32],
+            encryption_key_stoc: vec![0u8; 32],
+            mac_key_ctos: vec![0u8; 32],
+            mac_key_stoc: vec![0u8; 32],
+            sequence_number_ctos: 0,
+            sequence_number_stoc: 0,
+        }
+    }
+}
+
 impl EncryptionContext {
     /// 创建加密上下文（从SessionKeys）
     pub fn from_session_keys(keys: &SessionKeys) -> Self {

markbase-core/src/ssh_server/server.rs

@@ -3,10 +3,11 @@
 
 use crate::ssh_server::version::VersionExchange;
 use crate::ssh_server::packet::{SshPacket, PacketType};
-use crate::ssh_server::kex::{KexProposal, KexResult};
+use crate::ssh_server::kex::{KexResult, KexProposal};
 use crate::ssh_server::kex_complete::{KexState};
 use crate::ssh_server::auth::{AuthHandler, AuthResult};
 use crate::ssh_server::channel::{ChannelManager};
+use crate::ssh_server::cipher::{EncryptionContext, EncryptedPacket};
 use anyhow::Result;
 use log::{info, warn, error, debug};
 use std::net::{TcpListener, TcpStream};
@@ -85,6 +86,8 @@ fn handle_connection_complete(stream: TcpStream) -> Result<()> {
     perform_complete_kex_exchange(&mut stream, client_version.clone(), kex_result, server_kexinit, client_kexinit)?;
     info!("Key exchange completed, encryption channel ready");
     
+    let encryption_ctx = EncryptionContext::default();
+    
     // Phase 5: SSH认证（参考OpenSSH auth2.c）
     let mut auth_handler = AuthHandler::new()?;
     let auth_user = perform_ssh_auth(&mut stream, &mut auth_handler)?;
@@ -130,24 +133,20 @@ fn perform_complete_kex_exchange(
     kex_result: KexResult,
     server_kexinit: SshPacket,
     client_kexinit: SshPacket,
-) -> Result<()> {
+) -> Result<EncryptionContext> {
     info!("Starting complete key exchange flow");
     
-    // 1. 创建密钥交换状态
     let mut kex_state = KexState::new(
         client_version,
         "SSH-2.0-MarkBaseSSH_1.0".to_string(),
         kex_result,
     )?;
     
-    // 2. 保存KEXINIT payloads（用于Exchange Hash）
     kex_state.save_kexinit_payloads(&client_kexinit, &server_kexinit);
     
-    // 3. 接收SSH_MSG_KEX_ECDH_INIT
     let kexdh_init = SshPacket::read(stream)?;
     info!("Received SSH_MSG_KEX_ECDH_INIT");
     
-    // 4. 处理KEXDH_INIT并生成KEXDH_REPLY
     let kexdh_reply = kex_state.exchange_handler.handle_kexdh_init(
         &kexdh_init,
         &kex_state.client_version,
@@ -158,25 +157,22 @@ fn perform_complete_kex_exchange(
     kexdh_reply.write(stream)?;
     info!("Sent SSH_MSG_KEX_ECDH_REPLY");
     
-    // 5. 发送SSH_MSG_NEWKEYS
     let newkeys_packet = KexState::send_newkeys()?;
     newkeys_packet.write(stream)?;
     kex_state.newkeys_sent = true;
     info!("Sent SSH_MSG_NEWKEYS");
     
-    // 6. 接收SSH_MSG_NEWKEYS
     let client_newkeys = SshPacket::read(stream)?;
     kex_state.handle_newkeys(&client_newkeys)?;
     info!("Received SSH_MSG_NEWKEYS");
     
-    // 7. 验证加密通道建立
     if kex_state.is_encryption_ready() {
         info!("Encryption channel established successfully");
     } else {
         return Err(anyhow::anyhow!("Encryption channel not ready"));
     }
     
-    Ok(())
+    Ok(EncryptionContext::default())
 }
 
 /// SSH认证流程（Phase 5）