The app has been sending `flavor` since yesterday's change and PocketBase was
throwing it away. An unknown key in a create payload is dropped with no error, no
warning and HTTP 200 -- the same silent-drop behaviour already documented for hidden
fields in amber-app/CLAUDE.md. So the dashboard's "Podle varianty" row read
`neznámá` for every record while the client believed it was reporting the variant,
and the only way to notice was to query the stored rows and find the field absent.
Found by verifying instead of assuming: a real play/exit on the TV produced two
session_summary rows, both with flavor empty, on a build that definitely sends it.
Not folded into `meta`, though that needs no migration and the dashboard already
falls back to reading it there. The variant is a first-class dimension of every
record, exactly like platform and appVersion beside it, and burying it in json would
make the one query it exists for -- group errors by variant -- awkward for nothing.
Additive and nullable so existing rows stay valid. Validated on a clean local boot
of the pinned PocketBase against the real migrations directory: health 200, no
errors, and client_logs now reports the field.
