refactor(qbz-qt): split QbzAlbum and QbzArtist out of the God-object

Two singletons rather than one merged object, per the owner: each maps to the
view it backs. Registering them and deleting the duplicates from bridge.rs is
one change, because wiring one without removing the other compiles fine and
leaves two independent states with the view frozen and nothing in the log.

view_param_id goes with them. It had no consumer in QML, verified, and none in
Rust once the two opens stopped writing it — so it is deleted rather than
carried into a new bridge for symmetry's sake.

bridge.rs is down to three domains: settings, search and playlist.

cc

crates/qbz-qt/build.rs

@@ -35,7 +35,7 @@ fn main() {
         .qt_module("QuickControls2")
         .qml_module(QmlModule {
             uri: "com.blitzfc.qbz",
-            rust_files: &["src/bridge.rs", "src/session_bridge.rs", "src/shell_bridge.rs", "src/player_bridge.rs", "src/queue_bridge.rs", "src/home_bridge.rs", "src/viz_bridge.rs", "src/local_bridge.rs", "src/library_bridge.rs"],
+            rust_files: &["src/bridge.rs", "src/session_bridge.rs", "src/shell_bridge.rs", "src/player_bridge.rs", "src/queue_bridge.rs", "src/home_bridge.rs", "src/viz_bridge.rs", "src/local_bridge.rs", "src/library_bridge.rs", "src/album_bridge.rs", "src/artist_bridge.rs"],
             qml_files: &[
                 "qml/LoginScreen.qml",
                 "qml/Main.qml",