Fix: Client log dialog stops updating past edit-control default limit

The Win32 EDIT control caps text at ~32K/64K chars by default, so the
client log dialog silently stopped accepting appends long before the
512KB truncation logic could run. Call SetLimitText(0) in both
CClientLog and CActivityDialog to lift the cap.

Also unify newline handling in Logger: each entry now ends with exactly
one '\n' at the source, so the in-memory ring-buffer dump (used by the
TCP log query) splits into lines correctly instead of relying on every
Mprintf caller ending its format with '\n'. writeToFile drops the extra
std::endl accordingly.

Additionally fix a CFont leak in CClientLog::OnInitDialog by moving the
font to a member.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/2015Remote/CActivityDialog.cpp

@@ -39,6 +39,8 @@ BOOL CActivityDialog::OnInitDialog()
     m_editLog.SetFont(&m_font);
     // 重建为 Unicode 编辑框：这是 ✻/✦ 能正确显示的关键。重建时已保留上面的字体。
     RebuildEdit(m_editLog);
+    // 解除 EDIT 控件默认约 64KB 长度上限，否则大快照经 SetWindowTextW 会被静默截断。
+    m_editLog.SetLimitText(0);
     return TRUE;
 }