MeshChat V5 - Linux

FIRST RUN:
Run ./INSTALL_AND_RUN.sh.

That single installer will:
1. Reuse Python 3.10 or newer when available.
2. Install Python, tkinter, and venv through apt or dnf when missing.
3. Create MeshChat's private virtual environment.
4. Install and verify required packages.
5. Start MeshChat.

LATER:
Run ./run.sh. If setup is incomplete, run.sh starts the installer automatically.

Server: chat.meshnet.bespace.one:443 with mandatory TLS verification.
Account data remains in MeshChatData. Received executables are never run automatically.
