Relocates CastState (struct + impl) from cast/commands.rs to
cast/state.rs, and DlnaState (struct + impl) from
cast/dlna/commands.rs to cast/dlna/state.rs.
Both types are consumed by commands_v2/library.rs (and the legacy
Tauri commands themselves) via the existing re-exports in
cast/mod.rs and cast/dlna/mod.rs. The re-exports are updated to
source from the new state modules, and each commands.rs re-exports
its state type so historical
crate::cast::commands::CastState / crate::cast::dlna::commands::DlnaState
paths continue to compile.
This unblocks future deletion of cast/commands.rs and
cast/dlna/commands.rs in a later cleanup step (the
#[tauri::command] functions in those files are already
unregistered and have zero Rust call sites).
cc
vicrodh
ac44b8a713