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.
Keep a running companion-remote host's crypto identity in sync with the
active profile: subscribe to PlexHome/connection/join streams and rebuild
auth contexts (restarting the broadcast when they change) so a removed
home user or revoked borrowed connection stops controlling the host.
Serialize host start/stop/crypto-rebuild through a lifecycle lock, clean
up peer subscriptions before re-listening, and guard the replaced-client
onDone against clobbering the new client's session. Drop the context.mounted
guards that aborted an app-level host start, fix the DiscoveryView
init-flash/stuck-on-throw, and delete the dead initialize*Crypto helpers.
edde746