fix(socket): forward CLibSocket::OnLost(int) to CEMSocket::OnClose so eD2k server/peer disconnects actually fire - #906

Fixes #905. Likely also resolves #393 (the long-standing "search hangs after server goes away") as the upstream cause.

The asio backend's HandleRead dispatches both clean close (FIN, bytes_transferred==0) and reset/read-error via PostLostEvent() → socket->OnLost(0) through the CLibSocket vtable (LibSocketAsio.cpp:638-655). The CLibSocket::OnLost(int) default is an empty no-op. The eD2k path classes — CServerSocket → CEMSocket → CEncryptedStreamSocket → CSocketClientProxy → CProxySocket → CLibSocket — never overrode it, so peer FIN / RST was silently dropped on this side.

This is the eD2k twin of the EC bug fixed in e8462d619 / 4756556f2 / a6351ce70 (refs #757), which added CECMuleSocket::OnLost(int) forwarding to the EC-side CECSocket::OnLost(). Same shape, different leaf chain.

Symptoms before the fix

• eD2k server quits / drops connection → CServerSocket stays at CS_CONNECTED forever; next search hangs (mifritscher2's amule does not handle server connection aborts. #905 reproducer).
• Peer drops the file-transfer TCP connection → CClientTCPSocket stays ES_CONNECTED; the upload slot stays held by a dead CUpDownClient; transfers show 0 KB/s until some unrelated timeout reaps it.

The fix

Override OnLost(int) on CEMSocket to call OnClose(int). OnClose is virtual, so dispatch reaches the per-class teardown:

• CServerSocket::OnClose → SetConnectionState(CS_DISCONNECTED) → serverconnect->ConnectionFailed() → cleanup + auto-reconnect.
• CClientTCPSocket::OnClose → Disconnect() → releases the peer and frees the slot.

Both teardown paths already existed for the (now-defunct) wxSocket close hook; this just wires the asio path into the same plumbing.

Also adds the override keyword to seven adjacent CEMSocket members (OnError, OnSend, OnReceive, OnConnect, GetLastCalledSend, SendControlData, SendFileAndControlData, GetNeededBytes) that were missing it, to silence the -Winconsistent-missing-override warnings my new override would otherwise have spread across the file. All seven are legitimate overrides (verified against CLibSocket, CEncryptedStreamSocket, ThrottledFileSocket).

Test plan

• macOS local build (Apple Silicon, Homebrew) — clean.
• @mifritscher2 — would you mind retrying your original amule does not handle server connection aborts. #905 reproducer (amule + JEmule, search → quit server → re-search) against this branch? Build instructions are in the issue comment. With the fix you should see the "Connection lost" log line within a tick of the FIN, the connection state flip to disconnected, and the search request not get queued onto a half-closed socket. Auto-reconnect (if enabled) should kick in immediately.