OGPU wipes user://plugins/<id>/ (and everything inside it) whenever a
plugin is updated or re-extracted, so storing butler and butler.db under
user://plugins/itch/assets meant every version bump deleted the binary
and its login session. Store them in persistent user://butler instead,
and migrate any leftover install from the old location.
Godot JSON.parse decodes every JSON number as a float, so integer ids
(7670) round-trip through JSON.stringify as 7670.0, which Go's int64
fields reject with RPC error -32700. Normalize at the parse boundary so
profile/game/upload ids serialize correctly.
Also drop the nonexistent 'fresh' parameter from Fetch.ProfileOwnedKeys.
