Extracts the repeated toolbar fade into a single ToolbarScrim widget, folds
duplicated request/retry handling in the media server HTTP client, and
collapses the parallel playback-source, download-manager and live TV helper
paths into shared implementations.
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.
Drops dead code across services, models, utils and widgets, including the
connection auth service, which had no implementer, and the Live TV DVR
provisioning models, which had no caller.
Tests that only covered deleted behaviour are removed or trimmed. No
behaviour change.
Resolve platform, hardware model, and friendly device name once via a
shared DeviceIdentityService and send them to both backends: Plex gets
a real X-Plex-Platform plus X-Plex-Device/X-Plex-Device-Name (shown as
Player in dashboards/Tautulli), Jellyfin gets the device name in the
MediaBrowser auth header. Transcode and live-TV decision requests keep
their pinned platform names, which Plex validates server-side.
close#1270
edde746