Capishot portable mode

While this file sits next to capishot.exe, Capishot keeps its preferences, brush presets,
crash-recovery autosaves, downloaded AI models and startup state in the CapishotData folder beside
it, and writes nothing to %APPDATA% or %LOCALAPPDATA%. Copy the whole folder to move Capishot with
its settings.

Delete this file to use the normal per-user folders instead: %APPDATA%\Capishot for settings,
%LOCALAPPDATA%\Capishot\Recovery for crash-recovery autosaves and %LOCALAPPDATA%\Capishot\models
for AI models. If CapishotData can't be written (for example on a read-only drive), Capishot says
so and uses those folders instead.
