Fix Windows compilation error with socket close() function

[Copilot]

Problem

When compiling on Windows 10 using MinGW, the build fails with the following error:

error: 'close' was not declared in this scope; did you mean 'fclose'?

This occurs in src/dllama-api.cpp at line 563 and several locations in src/nn/nn-network.cpp. The issue prevents Windows users from building both dllama and dllama-api.

Root Cause

On Windows, sockets must be closed using closesocket() from the Winsock2 library, not the POSIX close() function. While the codebase already has conditional includes for Windows vs Unix socket headers, some socket close operations were not wrapped with platform-specific preprocessor directives.

Solution

This PR adds platform-specific handling for socket close operations following the same pattern already established elsewhere in the codebase:

• Windows (#ifdef _WIN32): Uses closesocket()
• Unix/Linux (#else): Uses close()

Changes

• src/dllama-api.cpp: Fixed client socket close after HTTP request handling
• src/nn/nn-network.cpp: Fixed socket close operations in:
  • closeServerSocket() function
  • NnNetwork::serve() method
  • NnNetwork::~NnNetwork() destructor

Testing

✅ Verified compilation on Linux for both dllama and dllama-api targets - all builds succeed with no errors or warnings.

Fixes #234

Related Issues

This follows the same pattern used for Windows compatibility in other parts of the codebase (e.g., lines 73, 194, 208 in nn-network.cpp).

Original prompt

please try to fix this issue: @b4rtaz/distributed-llama/issues/234

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