fix(webui): do not expose the Flask debug console on 0.0.0.0 by default

[hexonal]

Both webui entrypoints hard-code app.run(debug=True, host="0.0.0.0", port=7070).

Why this matters

debug=True enables the Werkzeug debugger. When an unhandled exception occurs, that debugger serves an interactive console that executes arbitrary Python in the server process — and host="0.0.0.0" publishes it to every machine on the current network. The README lists the webui as a local demo, so in practice this runs on laptops that join cafe, hotel and office wifi.

Werkzeug does require a PIN for the console, and it is printed to the terminal — but the PIN is derived from machine-stable inputs, and the debugger has a long history of PIN-bypass writeups. Either way, an unauthenticated remote endpoint whose failure mode is remote code execution should not be the default for a demo UI.

Note on scope

webui/app.py and webui/run.py each call app.run themselves. Patching only app.py would leave the problem in place for the path the README lists first (python run.py), so this changes both.

Fix

Defaults chosen for a laptop rather than a server — bind loopback, debugger off — with both still reachable for deliberate use:

KRONOS_WEBUI_HOST   default 127.0.0.1
KRONOS_WEBUI_PORT   default 7070
KRONOS_WEBUI_DEBUG  default 0, set to 1 to re-enable the debugger

Anyone who was intentionally serving to a LAN sets KRONOS_WEBUI_HOST=0.0.0.0 and is exactly where they were. Anyone who was not is no longer publishing a remote console without knowing it. The bound address is now printed on startup so the actual behaviour is visible rather than assumed.