[GUI] MinecraftClientGUI overhaul — dark theme, multiboxing, filters, logs

[AnonBOTpl]

Summary

This PR is a complete overhaul of the existing MinecraftClientGUI project
which has been unmaintained for some time.

The GUI has been fully rewritten while keeping 100% compatibility with the
existing MinecraftClient.exe core — no changes to the core project were made.

Screenshots

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What changed

• Replaced TabControl with a fully custom dark tab bar — eliminates all
  white system borders and flickering
• Each tab has a ✕ close button
• Log filter bar per tab: All / Chat / System / Errors
• Auto-save session logs to logs/<nick>_<date>.txt
• Connection uptime timer (HH:MM:SS) per tab
• Bot status indicator — green (connected) / red (disconnected)
• Auto-scroll toggle checkbox per tab
• Dark ComboBox with custom draw — no white dropdown backgrounds
• Email addresses trimmed to username in tab title
• Macro buttons redesigned with colored accent bar
• EN/PL language switcher made clearly visible
• Bottom chat input padding fixed

Compatibility note

This GUI is Windows-only as it uses WinForms with user32.dll
and uxtheme.dll for dark mode rendering. The original GUI was also
Windows-only, so this does not introduce new platform limitations.

Testing

Tested on:

• Windows 10 / Windows 11
• Minecraft 1.20.4 (MCC build 285)
• Multiple simultaneous accounts (multiboxing)