Focus chrome was implemented twice, once in the focusable wrapper and once
in the focus builders; both now go through FocusChrome. TvColorPicker's
channel row was a copy of TvNumberSpinner and is now that widget in compact
density.
Also trims unused helpers and fields and simplifies the Jellyfin browse
paths.
Introduces shared seams for paginated views, D-pad reorder, media control
routing, async singletons and the device method channel, then points the
open-coded copies at them.
Also removes unused models and duplicated provider/server plumbing, folds
the twice-implemented artifact store in the server, and factors the
repeated Flutter toolchain prologue in CI into a composite action.
Badge the mobile Library options icon with a dot while filters are
active, and replace the "This library is empty" state with a
"No items match the active filters" message plus a reset button.
close#1470
edde746