Feat: One-way TLS transport for the MFC server

Add optional one-way TLS to the MFC server (server/2015Remote) so the device
port can serve both TLS clients and legacy plaintext clients on the same port,
mirroring the Go server.

Server: on a connection's first bytes, sniff for a TLS ClientHello (0x16 0x03
+ handshake type 0x01). When [tls] Enabled=1 and the identity loads, hand the
socket to a short-lived blocking handshake thread (Option A) running Schannel
AcceptSecurityContext, then decrypt on recv and encrypt on send; plaintext
connections replay the sniffed bytes straight into the existing parse path, so
the plaintext code path is otherwise unchanged. The identity is loaded once
from [tls] CertPath/KeyPath as PEM + CNG (PKCS#8) — the same key pair the Go
server uses — and a missing [tls] section, an empty value, or a load failure
leaves plaintext serving intact and fail-closes any TLS ClientHello.

Also fix two transport-reliability bugs that surfaced end-to-end:
- send path: encrypt only the freshly appended plaintext tail and post a
  single IOWrite wake-up guarded by a bSendPending flag, so back-to-back small
  sends (terminal resize -> COMMAND_NEXT -> resize) no longer run concurrent
  WSASends over the same mutable buffer (client saw DecryptMessage failures,
  with WSAGetLastError() = 6001 / ERROR_DECRYPTION_FAILED);
- client Recv: keep the handshake's unconsumed tail bytes in m_raw and drain
  them before the next recv, and log the real SECURITY_STATUS on
  DecryptMessage failure instead of the stale Winsock error.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/Buffer.h

@@ -130,6 +130,11 @@ public:
     // 确认写入完成，更新内部指针
     VOID CommitWrite(ULONG writtenSize);
 
+    // 截断缓冲区到指定有效长度（仅回退写指针，不移动/释放底层内存）。用于「尾部明文替换为
+    // 密文」：TLS 下 OutCompressedBuffer 追加明文后需换回密文，用此接口避免 ClearBuffer 的
+    // DeAllocateBuffer 释放正在被异步 WSASend 引用的底层内存。
+    VOID TruncateBuffer(ULONG effectiveLen);
+
 protected:
     PBYTE	m_Base;
     PBYTE	m_Ptr;